The broad executive action on immigration that President Obama announced on Thursday night could shield nearly half of the estimated 11 million undocumented immigrants now believed to be in the U.S. from deportation.

But the move is much bigger than that.

The president is also directing the government to fundamentally reshape its priorities for enforcing immigration laws by focusing more intensely on removing criminals rather than families, overhauling immigration courts, and making changes to the high-skilled visa system.

Under the plan, the bulk of the estimated 5 million people who could be protected from deportation would be parents of U.S. citizens or green card holders who have lived in the country for more than five years. According to an analysis by the Migration Policy Institute, as many as 3.7 million undocumented immigrants could fall into this category; beginning next spring, they could register with the government, undergo a background check, start paying taxes, and gain protected status for up to three years.

Another 290,000 immigrants who were brought to the U.S. illegally as children would also be newly protected under an expansion of Obama's original Deferred Action for Childhood Arrivals (DACA) program. The administration is eliminating the age cutoff for DACA, which had been open only to people under 31, and it is allowing immigrants to apply if they have lived in the U.S. since 2010, not 2007 as before. The changes will increase the number of people eligible for that program to about 1.5 million, according to MPI. The White House says another 1 million immigrants would be newly protected from deportation under the other reforms in the president's directive. The policy institute estimates that the total number of undocumented immigrants now in the U.S. is 11.4 million people.

By the Numbers: The President's Plan

Data: White House and Migration Policy Institute

Who won't get covered? For starters, anyone who has come to the U.S. illegally within the last five years cannot apply, and unlike some congressional proposals, it will not allow people who have already been deported to re-enter the country. For reform advocates, the biggest exclusion is for parents of immigrants who gained protection under the 2012 DACA program, which the White House deemed would exceed the president's legal authority. And unlike the Senate-passed immigration bill ignored by the House, those protected from deportation will get only a temporary reprieve that could be reversed by Obama's successor, not a clear path to citizenship or permanent legal status.

Beyond the deferred action programs, Obama is also directing the Department of Homeland Security to make significant changes to how it enforces immigration laws. There will be more agents at the border, as well as structural changes to Immigration and Customs Enforcement, or ICE, to make its personnel closer in line with traditional law enforcement officers. Legal immigrants will also have more flexibility to travel to their countries of origin, and those who are working under H-1B visas will be able to change jobs more easily and get employment visas for their spouses.

The administration plans to move cases involving immigrants and families with no criminal history down the list of deportation priorities so that the government can focus on "national security threats, serious criminals, and recent border crossers." And DHS Secretary Jeh Johnson is throwing out a program known as Secure Communities that has long been a source of angst among immigration advocates, who complained that it encouraged local law enforcement departments to round up people solely based on a suspicion that they were in the country illegally. Johnson is replacing that initiative with something called the Priority Enforcement Program, which will instead emphasize the removal of undocumented immigrants who have already been convicted of crimes.

"We’re going to keep focusing enforcement resources on actual threats to our security," Obama said in his speech on Thursday night. "Felons, not families. Criminals, not children. Gang members, not a mom who’s working hard to provide for her kids. We’ll prioritize, just like law enforcement does every day."