Census 2010 was taken using only a "short form" consisting of basic questions about age, sex, race, Hispanic origin, household relationship, and owner/renter status. The American Community Survey (ACS) has been designed to replace the Decennial Census "long form" beginning in 2010 and to provide demographic, housing, social, and economic data every year for the U.S., states, and local areas. ACS data for all geographical areas down to Block Group are now available.
A census (i.e., a complete count) of the people of the United States every 10 years is required for the purpose of dividing up the seats in the U.S. House of Representatives among the states by the Constitution in Article I, Section 2, Clause 3:
The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct.
and by Amendment 14, Section 2:
Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State [...].
Look for the Glossary within the American FactFinder Help system. Definitions for subjects and geographical areas are also provided in the technical documentation for each dataset. The Census Bureau also maintains a general Glossary.
"The American Community Survey (ACS) is an ongoing survey that provides data every year - giving communities the current information they need to plan investments and services. Information from the survey generates data that help determine how more than $400 billion in federal and state funds are distributed each year." (Source: Census Bureau, "Other Census Data")