DACA is a program created by President Obama. The name (Deferred Action For Childhood Arrivals) is somewhat misleading, as most participants are adults.
800,000 illegal immigrants have signed up (wow!), over 15,000 in Fairfax County. They get to stay in the US as long as they renew their participation every two years.
DACA gives illegal immigrants the right to work, obtain a drivers license, and in some localities, vote, among other benefits. Technically, it does not provide legal status, only defers deportation indefinitely.
To be eligible:
Enter the US illegally before 2007 AND before age 16, or
Enter the US illegally before June 15, 2012 AND be under age 31
Be in school, have a HS diploma, or be a military veteran (rare)
Have a "mostly clean" (undefined term) criminal record
You can apply by mail for $465.
One reason the participation rate is high is because false documentation to meet these requirements is easily obtained, and rarely checked.
The underlying problem is that Obama created the program without Congressional authority, making it unconstitutional.
It's a crisis now because ten states have threatened the Trump administration: Sunset DACA by September 5 or the states will try to end it in court, where they will likely win.
https://www.uscis.gov/humanitarian/consideration-deferred-action-childhood-arrivals-daca