How does the 25th Amendment work?
What is chain migration?
A key part of immigration talks concerns "chain migration," a term used by President Trump and other conservatives to describe "family migration" and "family reunification visas."
Trump has demanded an end to the program, and it is one of the four pillars the White House has laid out for immigration talks, along with a permanent solution to the Obama-era Deferred Action for Childhood Arrivals program, border security and the diversity visa lottery program.
Chain or family migration is a system that allows U.S. citizens and legal permanent residents to petition the government to allow their close relatives to immigrate to the United States.
There are two types of family migration categories in U.S. law: immediate relatives and preference categories.
Under either category, U.S. citizens or legal permanent residents may sponsor their foreign relatives for green cards.
Immediate relative petitions, which can include spouses, unmarried children under 21 years of age and parents of U.S. citizens, are not limited by quotas and usually take about a year to process, however, preference categories are subject to quotas and can take decades to fully adjudicate.
Preference categories include some relatives of U.S citizens, such as unmarried adult children and siblings; and spouses and minor children of legal permanent residents.
In 2017, 542,370 family-based visas were approved by the government.
Trump and critics of the program want to end family-based migration in favor of a merit-based system that would give preference for green cards to immigrants with certain skills.
Supporters of the program argue family-based migration makes sense because it unites families that are otherwise separated by borders, strengthening communities in the process. They see the term "chain migration" as offensive.
"[It's] offensive to me to use that word, right, because it's really about family reunification," said Rep. Luis Gutiérrez (D-Ill.), a prominent pro-immigrant advocate.
"It's about a mom bringing their children, about children bringing their moms, about husband and a wife, those are the visas they're going after," he said.
Nearly 4 million people are on the waiting list for family-based visas, according to the State Department. As a result, supporters of the program argue the quotas on these visas should be raised.
They also note that wait times can last years.
"If you're an older child from Mexico ... that wait right now is like 22 years," said Olsi Vrapi, an immigration attorney who's a member of the American Immigration Lawyers Association.