link to pdf From Educause

“A screencast is a screen capture of the actions on a user’s computer
screen, typically with accompanying audio, distributed through RSS. In the same way that a screenshot is a static representation of a computer screen at a point in time, a screencast captures what happens on a monitor over a period of time. The audio track can be the sound from an application being demonstrated, a narrative from the presenter, or background audio from
another application. Screencasts can be produced in various formats, and users generally watch them streamed over a network.”