The American Community Survey was created following the 2000 Census using questions formerly asked on the Census. The Census is distributed to every household in the United States every 10 years and asks just a few questions. The American Community Survey collects more information, including questions about population and housing characteristics. It is compiled every year from a random sampling of 295,000 addresses a month across the United States.
You could be contacted by the survey while your neighbor isn’t. Or, your household may never receive the ACS. The Census Bureau will notify ACS participants by mail and include instructions for completing the survey online or by paper. Some households may receive both the ACS and the Census 2020 survey. Households should complete both surveys.