Footing is a support structure used in construction. The footing is what the base of the walls lock into. The footing is wider than the walls and provides a support base for the foundation. It is under the earth and the larger the building, the deeper the footing. Footing is often made of concrete but in some cases it is also made of wood.
Footing. Image courtesy of http://en.wikipedia.org/wiki/User:Blacklemon67
1. Builder’s Comprehensive Dictionary (Robert Putnam, Reston Pub. Co., c1984) p.171