What is a screencast? A Screencast is a video you create that captures the actions you preform on your desktop. People create screencasts all the time to demonstrate a tool or for training purposes. Screencasts are also used in education to demonstrate something running on your computer to students (but it creates a video so students can watch it later or even before class).
If you are interested in creating screencasts for your class, I recommend taking a look at a post by the EmergingEdTech blog titled "Comparing 12 Free Screencasting Tools". Here, you can find the right tool for you or this can be a starting point to explore different tools and video formats in screencasting. These are also great tools for students to create content for class exercises too.
Click on the link below to see the matrix of screencast tools: