The Bureau of Census is more commonly known as the, uh...Census Bureau. The mission of the bureau is to be the nation's leading source of quality data about people and the economy.
You know them...they send random people to your door periodically, usually unannounced, to ask how many people live with you, how old they all are, if they're in school, income, etc. Often they carry a clipboard or older model of tablet (hey, it's the government...their equipment is always kinda run down).
The bureau may seem suuuuper snoopy, but they're really just trying to gather information about the people in each area to note trends (higher unemployment rates, for instance) or even to determine how much education funding that area needs (pretty much by a simple head count).
The last census was done in the U.S. in 2010, and it's done every 10 years. In 2020, the plan is to use the internet more this time, but given how often email addresses change and the fact that not everyone has one, we're betting you'll still see the clipboard parade out and about.