CNN  — 

The European Union is arguably the world’s most powerful union. And the Brexit referendum is the biggest decision Brits have faced in a generation.

So, you can guess why there’s such wailing and gnashing of teeth about Thursday’s monumental vote. But if you haven’t been paying attention, no worries.

No worries. Here’s everything you need to know to become an insta-pundit.

What is Brexit?

Britain + exit = Brexit. It’s the idea that the Brits may vote to leave the European Union. There are some strong commercial reasons to NOT do so, but the Brits don’t like all the “social” bits that go along with staying. (We’ll get to that in a minute). So, this week, the UK will vote on a referendum: Should I stay or should I go? And if it decides to bolt, things can get verrry messy.

Since then it’s been talks, disputes, finger-pointing and threats – just like your typical divorce.

But the UK and the EU finally might have reached an agreement in which they can finalize their split.

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What's next for Brexit?

Before you get to any of that, tell me why should I care?

If you’re a European nation: You have the most to lose – on so many fronts. Just under half of the UK’s exports go to the EU. Just over half of its imports come from the rest of the Union. All of that will be up for a renegotiation. Then, think about diplomacy. Whenever Europe’s done something useful on that front, the UK’s been in the driver’s seat. So, the EU loses a heavyweight.

If you’re the U.S.: The world’s already dangerous and volatile enough. The United States worries the unraveling of the union – a vital ally – will just unleash more instability. The UK’s also America’s seventh biggest trading partner. Why rock the boat on such a sweet status quo?

If you’re any other nation: The UK economy is the fifth biggest in the world. If all the awful scenarios that the “Don’t leave” crowd is predicting (more on that later) come to pass, think of the effect it’ll have on the world’s markets. Even if they don’t, the uncertainty is bad enough. Markets, you see, heart stability. And unstable markets = potential bad news for your country’s economy.

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What's at stake if a Brexit deal falls through

Ok, wait. Before we go any further: What’s the difference between England, Great Britain and the United Kingdom?

We sometimes use them interchangeably (and incorrectly). So here’s a quick geography lesson.

The United Kingdom is not a single country but a country of countries. It’s made up of four nations:

  • England
  • Scotland
  • Wales
  • Northern Ireland

Great Britain is the island which holds England, Scotland and Wales.

And England is the big dog. It’s the most populous part of the UK and holds its capital, London.

And what’s the EU?

The European Union is a group of 28 countries that decided it would be cool if its citizens could go about vacationing and trading with each other without worrying about all the red tape. Its roots date back to World War II. After six years of fighting, Europe was decimated. Economies were in the toilet. Old enemies had to accept the fact they’ll need to live with each other (like France and its old occupier, Germany). So, little by little, countries started forming partnerships. By the 1990s, we had the modern European Union. It represents half a billion people. The idea is: If you’re linked economically, you’re less likely to bicker and fight.

Its roots date back to the period after World War II. After six years of fighting, Europe was decimated. Economies were in the toilet. Old enemies had to accept the fact they needed to live with each other (like France and its old occupier, Germany). So, little by little, countries started forming partnerships.

By the 1990s, we had the modern European Union. It represents half a billion people.

The idea is: If you’re linked economically, you’re less likely to bicker and fight.

02:00 - Source: CNN
What is the European Union?

Sounds like a great idea. So what’s the problem with the EU?

It sounds like a happy marriage. But you know how that goes. When world events walk in, these countries all react differently. They fight over how to deal with refugees coming to their shores. They can’t agree on financial matters. They’re mad that some of them have to pony up more than others to bail out countries that are doing terribly. And this has given rise to anti-EU parties all across Europe.

02:02 - Source: CNN
Trump calls European Union a 'foe' of the US

Has a country ever left the EU before?

No country has, but the world’s largest island did. Greenland, which is part of Denmark, was part of the EU until it left in 1985. (The rest of Denmark stayed.)

The UK will be the first bona fide country to leave. Greece has thought seriously about it, though. That would be Grexit (another story altogether).

But think about the precedent that’s about to be set. When the UK leaves, other EU countries might start eyeing the door too. That means the EU could slowly fall apart. And that could have huge consequences for the economy and stability. (Remember when we talked about why the EU came into being in the first place?)

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How 'Brexit' could impact Greece

What’s UK’s beef?

Turns out untangling a 45-year marriage is not as easy as the Brexiters claimed it would be. The fear of creating some serious unintended consequences (economic or otherwise) is high, and many hurdles have yet to be overcome. The delays, the dangers and the constant bickering are now – just two months before Britain is due to leave – prompting some who voted for Brexit to change their minds, opinion polls suggest. Remember all those Brits Googling “What is Brexit?” the day after they voted for it?

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Brexit showdown bringing uncertainty to UK

What’s happening now? Why’s Brexit back in the news?

The UK’s always had an arm’s-length relationship with the EU anyway. (For instance, most of the EU nations use a common currency, the Euro. The Brits took a pass on that.) There are two things Team Leave EU is increasingly developing an allergy to. Thing 1: The money the UK gives the EU. Team Leave thinks $16.3 billion (that’s how much the UK paid in 2014) is way too high a membership fee to be a part of any club, and that it could go toward other stuff. Thing 2: All the EU rules and regulations. Earlier this year, Prime Minister David Cameron got the Brits a “special status” that exempts the UK from a lot of these rules. But that’s not enough for some folks.

But, under that plan, the UK would stay inside the EU’s single market and still be subject to EU laws and regulations until the end of 2020. That would give everyone enough time to … hammer out a future trade deal. So yes, probably two more years of the same.

So, essentially the UK would leave the EU by basically staying in it for another two years. That’s clear, right?

Oh, one other important thing: The agreement guarantees protections for the more than 3 million EU citizens in the UK, and over 1 million UK nationals in EU countries to continue to live, work or study as they currently do.

04:15 - Source: CNN
Theresa May stands firm, defends Brexit draft

What’s one of the biggest sticking points?

The Irish “hard border.” Right now, the border between the Republic of Ireland and Northern Ireland is open. People (and trade) move between the two nations with ease. There are fears that could change in a Brexit divorce. The Republic of Ireland is in the EU. But Northern Ireland, which is part of the UK, won’t be in the EU trading bloc after the split. Normally that would require a so-called “hard border,” with checkpoints, border crossings and other infrastructure. Those could seriously slow trade and other economic activity.

Irish politicians also fear they could escalate tensions and raise the need for security to be in place. (No one wants a return of the Troubles in which more than 3,600 people were killed.) Pro-Brexit types in Great Britain would be OK with a hard border if it means the UK can negotiate its own trade deals with other countries. So, the draft agreement maintains the status quo on the Irish border while the two sides work out a permanent solution.

Still confused? Here, we’ll explain it with Lego.

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Explaining the EU customs union with Legos

So did the agreement pass?

Nope. On January 15, the UK Parliament voted a resounding rejection of Theresa May’s proposed Brexit plan. At 432 to 202, it was a historic defeat, with more than a hundred “no” votes cast by members of May’s own party.

The resounding defeat even led Jeremy Corbyn, leader of the opposition Labour Party, to trigger a vote of no confidence in Theresa May, which could have led to a general election. But May survived the vote, clinging onto power by the skin of her teeth – yet again.

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Ready for school? Kids explain Brexit

What next, then?

May is still trying to salvage her deal, and could put it before parliament again with a few tweaks – but it doesn’t look likely that any version of her agreement would be able to pass. In theory, then, Britain would end up leaving on March 29 under the “no deal” scenario that businesses are fretting so much about.

But parliament might even block that from happening, and instead force May to extend Article 50 – essentially kicking the can down the road, and making that date circled in red on the Brexit calendar pretty irrelevant after all.

That would give everyone more time to figure out a way forward – whether it’s holding more votes on May’s deal, securing a dramatically new agreement or throwing it all back to the people, in the shape of a general election or second referendum.

And then there’s the nuclear option – Britain could, technically, revoke Article 50 and pretend the whole thing never happened. That’s according to the European Court of Justice, which ruled in December that such a move would be legal. But that would hugely anger the millions of Brits who voted for Brexit – so don’t expect May to take that path any time soon.

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Businesses growing concerned over no-deal Brexit

Will there be a re-vote on the referendum?

Some big-time Brits like former PM Tony Blair have been calling for this, but no, there are currently no plan to take this back before voters. British Prime Minister Theresa May has slammed the door shot on that idea, saying a new vote would be a “gross betrayal” of democracy. Her draft agreement will be voted on by the parliaments of the UK and the EU, and that’s that, she’s said.

That said, the campaign for a second go – also being called a People’s Vote – has gathered pace, especially since May’s deal was so emphatically defeated. Plenty of Labour MPs have been lobbying Corbyn to support it, and if that happens, it could start looking like the easiest way out of the mess.

Still, parliament would have to approve a second referendum and decide what options it would entail – which could itself be a lengthy process.

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Britain's Brexit agreement deadline is near