The painted shader 'absolute' setting means that the brush will react accordingly to the depth your brush reaches 'into' the preview in 3D space, i.e. if you paint close to the camera with a 10m brush and then extend the stroke further into the scene, the brush will appear to shrink because it's keeping the same 'absolute' 10m scale, in relation to the surface it is painting on.
'View relative' means preview window relative, meaning that the brush is the same size in your preview, regardless of what 'depth' into the 3D space you paint.
Another good point to note, using the 'absolute' brush can crash the program erratically when painting on the sky. If you use 'view relative', it doesn't crash.