http://www.techradar.com/news/the-best-free-screen-recorder

Fancy showing other people how to play big name games on YouTube? Would you like to make demos to show off your apps, or to teach others how to use specific software? Then you need a screen recorder, and there are some excellent options available completely free.

The simplest screen recorders simply capture what's on your screen and save it in AVI format, but the more advanced free tools also offer editing, picture-in-picture, live streaming, and gameplay optimization.