How do you define a hero?

"CNN Heroes: An All-Star Tribute" airs at 8 p.m. ET/5 p.m. PT Sunday live on CNN. During the show, Dr. Sanjay Gupta will provide exclusive backstage interviews that can only be seen on CNN.com and your mobile device.

(CNN) -- Giving support to young war widows. Providing something as simple as soap to thousands to stave off disease. Taking children from the slums to the soccer fields.

These are just some of the actions of ordinary people changing the world. They and others will be honored on "CNN Heroes: An All-Star Tribute," and a Hero of the Year named on Sunday night. (Meet the CNN Heroes.)

But what exactly is a hero? Over the past few months, some high-profile people have weighed in:

"A hero to me is somebody who puts themselves last, who puts everything on the line for other people," says actress Lucy Liu.

Hip-hop artist Common describes a hero as someone "who is able to take whatever talent, gift, personality, quality and utilize it to help build others."

"Anyone can be a hero," says actor Rainn Wilson of "The Office." "It just takes a little bit of work." He is helping 2007 CNN Hero Aaron Jackson improve the lives of Haitian children.

What do you think? How do you define a hero? Who has been an everyday hero in your life? What are ways you or your community could make a difference? Share your comments below.