A fault is a fracture in the Earth's crust whose sides have moved in relation to each other. The San Andreas fault is a lateral fault. Lateral movement occurs when rock on one side of the fault slides horizontally past rock on the other side, with very little vertical motion. The San Andreas is a right-lateral fault.
Geologists use the term right-lateral to describe the direction the fault moves.
If you were standing on one side of a right-lateral fault and facing the fault, a person standing on the opposite side would move to your right during an earthquake. The San Andreas fault is also the boundary between the Pacific and North American tectonic plates .