Don't question it, try it :p
Its a set of terrain textures.
You paint them on the ground.
To change which set you ate using you run the test game (little rocket icon) then when in test press tab twice, you will see a drop down menu for terrain, choose it from there, then escape out of test mode, and you will now be able to use the new textures.
i5, NV960 2GB, 16GB memory, 2x 2TB Hybrid, Win10.
i3 , Intel integrated graphics, 6GB memory, 512GB Generic SATAIII Win8.1.
Intel Celeron (duel Core), Radeon integrated graphics, 4GB memory, 180gB Generic SATAII, WinVista.
Q6600, Intel integrated graphics, 8GB memory, 512GB Generic SATAII, Win7.