Terrain: Detail resolution per patch

Hi, i'm about to create a terrain in Unity and i want to know what does the "detail resolution per patch" in terrain's options stand for and i didn't find any info about that so far. What's the difference between 8 and 128 values for example and how much it affects performance?

I found this to be quite helpful in understanding detail resolution per patch.

Your terrain is a big square and the detail per patch (8-128) is how many detail meshes can be in one space square of the terrain. If your terrain is too big this can cause some weired issues with the detail per patch but as long as your detail resolution is quite higher than your detail patch you should not have many problems!

Hope this helps you guys and anyone coming around looking for the answer!