@davidroberson Weightmaps, masks, channel masks are all the same thing. It’s a black and white mask you can either export from wm as a separate weightmap, or as an RGBA image, containing 4 such weightmaps (also sometimes called a SPLATMAP) as individual channels of said image. This can later be used to set up your material, or to scatter vegetation etc, in a game engine or 3D program.
For example, this one. I used masks/weightmaps exported from wm to build this material (though I did it inside wm itself, but could have been done the same way in blender).
Hope this explanation helps!