Shaped, memory foam filled saddle pads provide cushioning for both the horse and rider.
A shaped (or "numnah") saddle pad is saddle shaped, and is designed to be used alone, or with a square saddle pad. A shaped / numnah pad should only be slightly visible below the saddle.
Memory foam is an open cell, polyurethane material that molds to the body and prevents pressure sores. The drawback to memory foam is that it is quite heavy, and expensive.