The Trump administration's attempted changes to immigration and refugee policy highlight a complex system that foreigners must navigate to settle in the United States. The terminology, procedures and rules can be confusing.

Here's a primer:

Q: What is a refugee?

A: Federal law defines a refugee as someone who is outside the United States and demonstrates they face or would have faced persecution because of their race, religion, nationality, political opinion or membership in a particular social group in the country from which they are unwilling or unable to return.

Refugees are typically referred to the U.S. by the United Nations High Commissioner for Refugees, a U.S. Embassy or a nongovernmental organization. Once referred, it can take 18-24 months to process a refugee applicant.

A refugee is not someone seeking a better life for economic reasons.

Q: How many refugees come here?

A: The number of refugees that come to the United States has shifted with world events, according to Pew Research Center. The U.S. allowed nearly 85,000 refugees into the country during the most recent fiscal year, according to Pew.

The Obama administration last year set a goal to take in 110,000 refugees in 2017. The election's results changed that; the Trump administration says that cap will be 50,000.

Q: How are refugees screened?

A: Refugees go through a long process that includes security checks with the National Counterterrorism Center, the Federal Bureau of Investigation, the Department of Homeland Security and the State Department.

Applicants are interviewed by United States Customs and Immigration Services officers. Their fingerprints are collected and submitted against an FBI database, a DHS database and a Department of Defense database.

Refugees receive a medical screening, then take a cultural class and choose a location to settle.

Before traveling, refugees are screened once again by the U.S. Customs and Border Protection agency and the Transportation Security Administration.

Q: What is a green card?

A: Lawful permanent residents are often referred to as green card holders, because that's the color of the card they're required to carry at all times.

A green card holder is typically allowed in the United States for 10 years. After five years (or three with an American spouse), a holder can apply for naturalization and acquire citizenship.

Federal law requires refugees to apply for a green card one year after being admitted.

Q: How do people get green cards?

A: Immigrants must qualify for a green card through a job, through family members, through refugee or asylum status or by other special means.

Congress limits how many people immigrate to the U.S. via visas, which are issued by the U.S. State Department.

A U.S. visa is a travel document that allows people to enter the country. There are nonimmigrant visas for people wishing to stay in the U.S. temporarily and immigrant visas for those wishing to settle in the country.

There are more than 30 categories of immigrant visas, according to the State Department's website.

The State Department issued nearly 618,000 immigrant visas in 2016, according to the department's website. Most went to immediate relatives of U.S. citizens.

There is no limit to how many visas are issued for immediate family members, such as the parents, spouses of U.S. citizens and citizens' unmarried children under the age of 21.