Before I noticed this function, I always just drag texture on one surface of a prim to make one prim have multiple textures. However, when I edited the color of a prim, the whole prim color changed. Therefore, when I noticed this function, I was really happy.
This is in the building tool, under edit, “select texture”
When you click on select texture, you will see the whole object have a white outline, indicate that you are selecting the whole object texture.
Now, click on the surface you would like to change texture, you will see only one surface have the white outline and a white circle with a white x inside.
This white circle with a white x indicate how many texture repeated on this surface.
When you repeat the texture, there will have multiple white circle with a white x.
In this way, you can directly select texture on each surface, and one surface repeated times will not influence other surfaces.
If you didn’t use this selection, when you change the color of this function, the whole object color will be different.
However, when you select texture, you can only change one surface color!
This is a very simple but useful function for texture. For example when you are building a house, would like to have different texture on the inside wall and outside wall, and each texture on each surface repeating time might be different; try this method, this will help you to reduce many prims and texture uploading fee! :)