You Tube, not YTube, UTube, Uuuuu Tube .... what is YouTube? It can be anything you want it to be. Old movies, funny clips, news, training sessions, webinars, demonstrations, product reviews, cartoons, information, social networking, bla, bla, bla ... well if it's a video, it can go on YouTube!
Here are some advertising and development links for YouTube if you want to go in that direction. Great stuff ... for me!