YouTube is a website with user-generated content in the form of videos. When it first debuted it was awesome because there was nothing else like it, and it had great content. Now the site is nothing but ads, fat invalids ranting that the Mexican at McDonald's screwed up their order, and underaged girls prancing around in their underwear while lip synching to Katy Perry. The only good videos are video game reviews, but YouTube took out "Games and Gadgets" category, so video game reviews are now scattered.
YouTube is also great for finding old metal videos and live footage of your favorite bands.