Screen recording is a great tool when it comes to gaming tutorials, software troubleshooting, or teaching your mom how to use Facebook. You can easily record your screen on a Mac:
In the menu bar, go to file > New Screen Recording
Hit the record button
Be sure to close any embarrassing windows BEFORE you do this!
To end, hit the stop button in your menu bar
QuickTime should open and replay your recording. You can save and edit from there!
So, yes, QuickTime has a purpose. Happy recording!