Most of the time, we
think of the Census as being the total population count of the United
States (or any area, for that matter). But, the Census Bureau-- a
division of the Department of Commerce, actually collects and
dissemenates data from several surveys, including:
Taken every ten years ending in a zero, it's mandated by the Constitution, partially in order to determine congressional representation and partly to figure out how to fund and organize social programs.