Nested Areas (Large to Small):
All Census data is provided for specific geographic areas. When looking for data, you must choose the dataset that contains your data, the specific variables you are interested in, and the geography for which your data is collected. Geographic areas (also known as summary levels) include legal (state, county, municpal) administrative (ZIP codes, school districts) and statistical (census tracts, census blocks, PUMAs) entities.
Census geography boundary files that you can download for use within a Geographic Information System (GIS)