Deferred Action for Childhood Arrivals (known as "DACA") is a program established by the Department of Homeland Security ("DHS") in 2012 that allows undocumented immigrants who were brought to the U.S. by their parents, as children, to avoid deportation by meeting certain stringent criteria. Specifically, to be eligible for DACA, immigrants had to be younger than 31 on June 15, 2012, arrived in the U.S. when they were younger than 16, and lived in the U.S. since 2007. The phrase "deferred action" is exactly what it sounds like-- DHS agrees to temporarily ignore someone's undocumented status and gives them the opportunity to apply for a work visa, which grants them temporary legal status like any other foreigner temporarily living in the U.S. for work.

There is no direct path to legal resident status or citizenship for a DACA recipient and it can be revoked at any time. But deferred action provides a modicum of relief to people who have grown up in the U.S., gone to U.S. schools, made U.S. friends, served in the U.S. military, paid U.S. taxes, and are otherwise Americans in all respects except on paper.

For more information about DACA and Dreamers see:
http://www.immigrationequality.org/get-legal-help/our-legal-resources/path-to-status-in-the-u-s/daca-deferred-action-for-childhood-arrivals/