What is the "bridge" in a song?

I know what the course is, and the verses. Basically i already know what it is but can someone post a link of a vid with a song and say when the bridge comes in for an example of one. cuz im writing a song and I need a bridge, but i dont neccisarily know what it is or how to write one. I watched this video on a basic song structure but didnt understand what the bridge is http://www.youtube.com/watch?v=v62mkJJPXVI&feature=fvw