Vegitation:
Maximum Shift Grass Grows On determines how much of a differnce in height grass is allowed to grow on. The Grass Base Color is the color for the grass which is then adjusted by Variation. The Variation adjusts the base colors lightness/darkness randomly as it places the color in the texture. The Rock Base Color is the color for the rock (or areas grass wouldn't grow) which is then adjusted by Variation. Variation, again adjusts the base colors lightness/darkness randomly as it places the color in the texture.

You can toggle on/off Change to Sand Below Height to change from grass to sand. The way the vegitation is made, sand will only be where grass could have been. It's understood that if grass couldn't grow because of the amount of slope, that sand wouldn't stay and that slope and would slide down. Again, sand has it's own color and variation.

You can also toggle on/off Change to Snow Above Height to change from grass to snow. Again, the way vegitation is made, snow will only be where grass could have been. Understanding that if grass couldn't grow becuase the slope is too steep, snow would slide off the slope.

Creation:
Create Texture will actually create the texture. It does not save the texture or blur it. After the texture is created it can be blured if you want. This is generally good to help soften the change in color. You may want to increase the Variation values of the vegitation if you are going to blur the texture a lot.