Alien - Any person not a citizen or national of the United States. [not suggested for current use]
Asylee - An alien in the United States or at a port of entry who is found to be unable or unwilling to return to his or her country of nationality, or to seek the protection of that country because of persecution or a well-founded fear of persecution. Persecution or the fear thereof must be based on the alien's race, religion, nationality, membership in a particular social group, or political opinion. For persons with no nationality, the country of nationality is considered to be the country in which the alien last habitually resided. Asylees are eligible to adjust to lawful permanent resident status after one year of continuous presence in the United States. These immigrants are limited to 10,000 adjustments per fiscal year.
Deportation - The formal removal of an alien from the United States when the alien has been found removable for violating the immigration laws.
Immigrant - See Permanent Resident Alien.
Legal Residents -- All persons who were granted lawful permanent residence; granted asylee status; admitted as refugees; or admitted as nonimmigrants for a temporary stay in the United States and not required to leave by January 1, 2009. Nonimmigrant residents refer to certain aliens who were legally admitted temporarily to the United States for specified time periods such as students and temporary workers.
Lawful permanent residents (LPRs) -- also known as “green card” holders, are non-citizens who are lawfully authorized to live permanently within the United States. LPRs may accept an offer of employment without special restrictions, own property, receive financial assistance at public colleges and universities, and join the Armed Forces. They also may apply to become U.S. citizens if they meet certain eligibility requirements. (See also Permanent Resident Alien below)
Naturalization - The conferring, by any means, of citizenship upon a person after birth.
Permanent Resident Alien - An alien admitted to the United States as a lawful permanent resident. Permanent residents are also commonly referred to as immigrants; however, the Immigration and Nationality Act (INA) broadly defines an immigrant as any alien in the United States, except one legally admitted under specific nonimmigrant categories (INA section 101(a)(15)). An illegal alien who entered the United States without inspection, for example, would be strictly defined as an immigrant under the INA but is not a permanent resident alien. Lawful permanent residents are legally accorded the privilege of residing permanently in the United States. They may be issued immigrant visas by the Department of State overseas or adjusted to permanent resident status by the Department of Homeland Security in the United States.
Refugee - Any person who is outside his or her country of nationality who is unable or unwilling to return to that country because of persecution or a well-founded fear of persecution. Persecution or the fear thereof must be based on the alien's race, religion, nationality, membership in a particular social group, or political opinion. People with no nationality must generally be outside their country of last habitual residence to qualify as a refugee. Refugees are subject to ceilings by geographic area set annually by the President in consultation with Congress and are eligible to adjust to lawful permanent resident status after one year of continuous presence in the United States.
Unauthorized Residents -- The unauthorized resident immigrant population is defined as all foreign-born non-citizens who are not legal residents. Most unauthorized residents either entered the United States without inspection or were admitted temporarily and stayed past the date they were required to leave.
All definitions are taken from the Dept. of Homeland Security website