The Planar brushes add the ability to flatten parts of your model, without creating overlapping geometry. By default, these brushes will flatten everything which is at the clicking level and aligned with the brush angle, by doing a click drag: if you click inside a cavity, everything which is above the click depth will be flatten. This means that if your click is on the top of a peak, nothing will be flattened as your cursor is already on the top of the model. The Imbed slider in the Brush >> Depth menu controls the depth of the stroke when using the planar brush.
The Trim brushes are based on the Planar brushes but provide a different behavior based on the normal of the surface or the screen working plane. Compared to the Planar brush which are restricted to a clicked point on the surface, or a defined path, the Trim brushes do not have these restrictions by default.
These brushes will allow you to sculpt hard surfaces in a freehand way.
The Polish brushes smooth, flatten and shine the surface so that it resembles polished metal.