How do people on youtube record tutorials they do on their computers for us to watch?

I only know of digital cameras and comcorders.How do people on youtube record tutorials they do on their computers for us to watch?
if u want to take videos ingame





den u can use d software called gamecam...





otherwise too u can use gamecam even when ur not ingame..


u can record ur work with it..


hers d link for game cam.





http://dl.phazeddl.com/899171/GameCam_1.4/L0rdW4r3zHow do people on youtube record tutorials they do on their computers for us to watch?
They don't have anything else to do.