I’m not understanding how the Mask brush works in Texture Paint mode and I couldn’t find documentation about it.
It seems to paint in the texture like a regular brush. How to use it?
What I’m looking for is to select and move an area in the texture like you do in the other image editors.
What I’m looking for is to select and move an area in the texture like you do in the other image editors.
Blender is not image editor, so don’t think that way.
Let me try to reformulate your question, Do you want the mask brush that will let you paint into just faces and stop you from painting in others? If yes then do this click the button that looks like cube with one side checker texture (tooltip is helpful). To select a face right click (LMB) to paint left click (LMB), so only selected faces will be affected. As long as i remember you cannot move an image in Blender but you can use stencil brush to paint any given image.
Hope this was kind of help 
I know about face masking. What I want is pixel masking and/or know what does this Mask brush.
The same question. What 2d mask brush actually do? How should it work?