Named after Pierre Bouguer - French physicist-hydrographer (1698-1758).
When a comet or asteroid collides at a high rate of speed interplanetary with the surface of Mars it creates an impact crater. Layers may be formed by a number of processes. On Earth rock layers are often formed under a lake or other body of water. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Mars large craters are named after deceased scientists, writers and others who have contributed to the lore of Mars. Small creaters (less than 60km) are named after small towns and villages.