To understand Obama’s next big immigration action, you need to understand his first

Before the end of 2014 — and possibly as soon as this week — President Obama is poised to announce broad executive action on immigration, including protection from deportation and access to work permits for up to 4 million unauthorized immigrants.

Obama’s rumored action will be unprecedented in its scale, but not in its form. It’s likely that the administration will be building on an existing program that gives relief to young unauthorized immigrants — the Deferred Action for Childhood Arrivals program, or DACA. (In fact, estimates that the president will end up protecting 5 million immigrants from deportation include the existing DACA program in the total.)

DACA has been around since 2012, but it’s more controversial now than ever — in part because of the attention getting paid to President Obama’s anticipated new proposal. Here are the basics of how the existing DACA program works — which might help explain how Obama’s new executive actions are going to work.

(For a deeper look at the DACA program, see my feature from this summer.)

Deferred Action for Childhood Arrivals, or DACA, is a program the federal government launched in 2012. It allows young unauthorized immigrants who meet certain criteria to apply for a commitment from the Obama administration for “deferred action” — that is, a commitment not to initiate deportation proceedings against the applicant — for two years. Successful applicants also receive a work permit.

The administration created DACA as a way to protect unauthorized immigrants who would have gotten legal status if the DREAM Act had passed Congress in 2010. (It passed the House, but failed to pass the 60-vote threshold for cloture in the Senate.)

Obama and immigration officials in his administration had been saying for years that they would not deport unauthorized immigrant students. But federal immigration agents weren’t getting the memo. So the administration stopped relying on passive protection from deportation, and allowed “DREAMers” to apply for protection themselves. (If you’re confused by this distinction, see my article here, which explains it in more detail.)

No. Under deferred action, an immigrant has a certain amount of time during which he or she won’t be deported. Deferred action also gives immigrants a number of important benefits, including the ability to get a work permit, a driver’s license (in most states), etc.

But deferred action is temporary, and must be renewed. Often in the past, the period before renewal was one year; under DACA, it’s two years. At the end of that time, the deferred action can be renewed.

And DACA recipients don’t receive what’s known as legal status — and that means they aren’t given a path toward a green card and eventual citizenship.

There have been plenty of executive actions to protect certain populations from deportation, but most of those haven’t used deferred action per se. However, deferred action has been around for a long time, and there are a few examples of presidents using deferred action to protect certain populations:

As of June 2014, 580,859 people had received deferred action under DACA — about half of the people who are estimated to be eligible. So it’s only been partly successful in reaching the population it’s intended to reach.

But for the people who have received DACA, it’s been a big success — removing the fear of deportation, and emboldening them to take leadership roles in the community. For a closer look at how the DACA program has worked so far, read my feature on DACA from August.

When DACA was first announced in 2012, many Republicans were critical of it — saying that President Obama should be waiting for Congress to make its wishes known on immigration, rather than protecting people Congress hadn’t decided to give legal status to. But most of those criticisms were muted. Mitt Romney, then the Republican nominee for President, avoided giving an opinion on the program for several months — and then declared that while he’d stop new people from applying for protection, he wouldn’t strip protection away from anyone who’d already received DACA.

But as Congress debated whether and how to pass immigration reform bills in 2013, DACA became a target for conservatives who supported maximal immigration enforcement, including the principle of “random deportations.“ And it became even more controversial in 2014, after it became clear that Congress wasn’t going to pass immigration reform, and that President Obama might be expanding deferred action to a larger group of immigrants. Part of the controversy over DACA now is tied to conservative opposition to the broader executive action the president is expected to take at the end of 2014.

It’s a little tricky to “defund” DACA, because US Citizenship and Immigration Services — the agency that runs the program — is funded almost entirely by application fees rather than by taxes. (To apply for DACA, immigrants have to pay $465 — and they have to pay the same amount two years later to renew it.)

However, House Republicans have tried to put conditions on a few government funding bills that would simply prohibit the Obama administration from continuing to implement DACA. In one iteration of this, passed by the House in 2013, the administration wouldn’t be able to implement any of its prosecutorial discretion policies to limit deportation — even by passively deciding not to deport certain categories of immigrants. In another iteration, passed by the House in 2014 as part of its response to the child-migrant crisis, the government would be prohibited from issuing DACA protections to any new applicants — including current recipients who’d need to renew their DACA grants after two years.