See the Overlay & Appearance options.

Project Paint

With Geometry occlusion active only exposed (not hidden by other mesh parts) pixels are affected. This also allows for 3D stencils to be used to mask out areas of the surface too.
With backface culling enabled you can only paint on the front side of faces.

Activates a view normal falloff which means that as faces point away from the view the brush strokes fade away to prevent harsh edges.

The normal angle at which the falloff begins.
Cavity Mask
Cavity masking means that the brush will be masked if there is a cavity or a hill on the mesh surface depending on the mesh options. The cavity algorithm is vertex-based.
Seam Bleed extends the paint beyond UV island bounds to avoid visual artifacts (like bleed for baking).
Amount of dithering when painting on 8 bit images.
Unified Settings

Brush options shared between the brush types.

Size, Color, Strength