Green Cards

A Green Card holder is a permanent resident who has been granted authorization to live and work in the United States on a permanent basis. As proof of that status, U.S. Citizenship and Immigration Services (USCIS) grants a person a permanent resident card, commonly called a "Green Card."

If you are an immediate relative of a U.S. citizen, you can become a lawful permanent resident based on your family relationship if you meet certain eligibility requirements

You are an immediate relative if you are:

• The spouse of a U.S. citizen;
• The unmarried child under 21 years of age of a U.S. citizen; or
• The parent of a U.S. citizen (if the U.S. citizen is 21 years of age or older).

You can become a permanent resident in several ways, including:

• Sponsorship by a family member or U.S. employer;
• Refugee or asylee status or other humanitarian programs; or
• Individual filing

Ref sources: 
https://www.uscis.gov/green-card/green-card-eligibility-categories   
https://www.dhs.gov/get-green-card