A green card holder is someone who has Lawful Permanent Resident (LPR) status, which means he or she is allowed to stay here permanently. If you are an LPR, you can work, but you cannot vote. The document is officially called an I-551 (Alien Registration Receipt Card or Permanent Resident Card).
To become a green card holder, you have to either: 1) be admitted here on an immigrant visa, or 2) be admitted here on a nonimmigrant visa and go through Adjustment of Status (AOS).
If you want to bring your fiancé or foreign national spouse to the U.S. so that he or she may get a green card, you most likely will need to receive a K-visa, come to the U.S. and then complete processing for permanent resident status.
People granted asylum or people admitted as refugees can also become green card holders.
Green card status may be taken away for certain crimes that can result in deportability or inadmissibility or lost through “abandonment.”
A Border Crossing Card (BCC) is an ID card for those who are lawfully admitted for permanent residence, or to aliens of Mexico or Canada for the purpose of crossing the border. This card also acts as a B1/B2 visa.
Green card holders may request or petition for certain family members to come to the U.S. as lawful permanent residents so that they, too, may receive a green card. This includes spouses (husbands and wives), unmarried children under 21, and unmarried sons and daughters of any age.
Green card holders who have been here at least five years and meet all the eligibility requirements may be eligible to become US citizens. If you file as a spouse of a US citizen, then you only need to have been here 3 years.