A screencast is a recording of your screen. Optionally, voice and video can be added, thus video highlights like red circles at mouse clicks or drawing on the screen are possible. This is a great way of recording a bug, UX, or generally showing workflows in action. Screencasts make it easy for us to understand what and where exactly an issue occurs as well as the conditions needed to reproduce the issue - e.g. a bug report (if it’s not obvious).
We use the browser extension Screencastify, but feel free to use the screencast program of your choice. You can find a quick tutorial of the program here, however just recording the screen will be sufficient in most cases.
After recording the screencast, just copy and paste the video link in Teamwork messages into the corresponding thread.