Fig 1. Sculpt Menu

Fig 1 shows you what you get when you use the <4> or <5> keys:

<4> - Push

Press and hold the <4> key to push in the surface at the mouse pointer location.

<5> - Pull

Press and hold the <5> key to pull out the surface at the mouse pointer location.

<G> - Sculpt Marked

 [more words here] 

<Shift-G> - Sculpt Marked Inwards

 [more words here] 

Fig 2. Settings

Additional Settings

If you click on the gray Sculpt button in the Brushes panel, then some additional settings are shown (see Fig 2). Click on the Sculpt button again to hide these away.

Shape 

Fig 3. Shape

Sets the shape of the push and pull brushes (see Fig 3).

Dir 

Sets a special direction for the push or pull action.

Off 

No special direction. All points are moved in the direction of the average surface normal at the mouse pointer location, and this is good for most sculpting work.

Eye 

All points are moved directly towards or away from the eye/viewer.

Out 

Each individual point is moved in the direction of the surface normal at that point.