There are three different federal censuses taken at intervals of 5 or 10 years. The Population and Housing Census is taken once every 10 years. The Economic Census and the Census of Governments are each taken every 5 years.
Besides those three censuses, the Census Bureau also gathers data using the American Community Survey, which is completed annually. Other surveys and the Economic Indicators are also the responsibility of the Census Bureau.
The data gathered by the Census Bureau serves several purposes. The data helps to determine how certain federal funds are distributed. It also helps to determine how many seats each state gets in the United States House of Representatives and determines what government services are needed in specific areas.