This tutorial is a basic overview of Werble's mask tool, which lets you erase or paint in regions of any layer. With a good grasp of the mask tool you'll be able to properly composite different layers together to create even more mind-blowing scenes!
In addition to general masking concepts, each facet of the mask tool is explained in detail, and demonstrated in the creation of a simple scene.
If you found this tutorial useful, check out the Advanced Mask Tool tutorial, which contains important advice on workflow and optimising your creativity. It builds on this same scene using more advanced ideas that will hopefully inspire you to go even further with your creations!
Advanced Mask Tool: https://youtu.be/f_uKAkml-gA