Photoshop layer masks overview.
Layer masks use an overlay that can be adjusted to work with people and objects that have irregular edges. Use feathering and refining tools to realistically select hair and fur.
Adjust your masks by painting on black and white. White areas will be affected by edits and black areas will not. Play with opacity and grayscale to change the degree to which your edits are applied.
Unlike a layer mask that’s manually painted on, vector masks use math to create pixel-perfect lines and edges for your selections. They’re great for architecture and areas that have straight lines.
To edit the selections you make with your masks, you can use any of the Photoshop tools you’re used to — such as Brush tools, Gradient tools, and Eraser tools.