Standard Brush

Standard: The Standard brush is the original basic ZBrush sculpting brush, and when used with its modifiers at their default values, it displaces outward the vertices over which it passes, giving the effect of adding clay to a sculpture. It can be used with all of the various brush modifiers, such as Strokes, Alphas, an edit curve, and so on. Pressing the Alt key causes the standard key to carve into, rather than build up, the model.

Elastic: Elastic works similarly to the Standard brush, but for some model types, is more accurate at maintaining the original shape of the surface as the surface is displaced. Experiment with both to see which is better for your work.

Displacement: Displacement works similarly to the Standard brush, but works to keep the details intact in such a way as to suggest that the form underneath has swelled or been displaced.