Screencasting is a great way for teachers to create a "how to" video, a flipped video for content acquisition, or personalized materials for their classes.  Students can also use screencasting for their own presentation needs.  Here are some suggestions:

Screencast-o-matic is a program that works best when downloaded and installed, although it can work inside your browser. 

If you are using Chromebooks, Screencastify is a popular choice.  It is an extension in your Chrome browser, and videos are automatically saved to your Drive. (Note: the free version is limited to video lengths of five minutes.)

For more information and a comparison of the two tools, read this blog entry.

Last but not least, Macbooks have a built-in screencasting option.  Click here to view a how-to video.