A screencast is a digital video recording that captures actions taking place on a computer display. Screencasts, which often contain voice-over narration, are useful for demonstrating how to use specific operating systems, software applications or website features.
Screencast production requires some kind of video capture software and a microphone. The software, which can be a desktop client or web-based service, captures and synchronizes the video and audio files and compresses the completed movie into a format that can be shared.
See also: screenshot
Tutorial screencast on how to create a quick, free screencast: