by John Martin, CNN

This Saturday, thousands of students across America will wake up, sharpen their number 2 pencils and proceed to take what could be the most important test of their lives - the SAT. There are some differences between the SAT that you probably took and the one students are taking this weekend. Here are five things to know about the big test.

1. What is the SAT?

The SAT is a college entrance exam taken by millions of students each year. The College Board, an association of colleges and high schools that creates and administers the test, says the exam tests skills and knowledge students acquire during high school and measures how that knowledge is applied, which many say is critical to success in college.

2. What is a perfect score on the SAT?

If you took the SAT before March 2005, you probably remember your score was out of 1600 points, 800 from math and 800 from reading. Today’s nearly four-hour test includes a critical reading section, a mathematics section, and a writing section. Each section is still worth 800 points; 2400 is today’s perfect score.

3. What’s on the test?

The old version of the SAT had analogies and math problems that asked you to compare two quantities. These kinds of questions are gone. Today, the critical reading section consists of two kinds of multiple choice questions. Test takers either have to fill in a missing word in a sentence, or answer questions based on a long or short passage. The math section consists of mainly multiple-choice questions. There are also a few questions where students have to solve a math problem and bubble in a numerical answer. The writing section also has multiple-choice questions that ask students to identify errors in writing or improve a piece of writing. That section also includes an essay that must be written in 25 minutes.

4. How is the SAT scored?

Most of the questions on the exam are multiple-choice. Each correct answer adds a point to a raw score. Wrong answers result in a 1/4 point deduction, which penalizes wild guesses. There are no points added or deducted for questions that are skipped. On math questions where students have to supply an answer, there’s no penalty for a wrong answer. The essay is graded by two graders; each one gives the exam a score from 1 to 6 and the two scores are added together.

5. Is the SAT the only option?

The SAT is required by many schools, particularly West and East Coast colleges in the United States. Many Midwestern states accept the SAT, but prefer the ACT, a different entrance exam. Some schools use class rank or grade point average (GPA) as admissions standards and do not require either test. Others may use it only for placement. According to FairTest, about 850 colleges make the tests optional for admission.