Here you can assign several textures (bitmaps) to your brush to create more realistic looking brushes. By default the brush constist of soft, blurred dots. You can change it here and use images.
First make sure that you have checked the Texture checkbox
Add one or more image files to the texture list with the + button.
You can remove them with the - button.
To change the order of the textures use the up or down arrows.
Texture Order controls the painting sort of the texture images if there's more than one texture in the list:
1234123 - textures selected as they apperas in the list (1,2,3,4).
After reaching the end of the list, the first goes again. (1,2,3,4)
1234321 - textures selected as they apperas in the list (1,2,3,4).
After reaching the end of the list, the order chagens to backwards. (3,2,1)
3142414 - randomly select the textures, this is the most natural way.
Skip First Dot won't paint the first dot. If you put down the brush by clicking with the left mouse button the texture painted but the program doesn't know yet the painting direction so the texture may lay to a wrong direction. To avoid this you can skip the first and the second will be lay fine.
High Quality renders the textures more accurately but slower. Use this if you have a fast PC and magnified the texture up and looks ugly by default.