A more thorough explanation:

An Alien Registration Card, also known as a green card, permanent resident card, or permanent visa, is an identification card issued by the United States Citizenship and Immigration Services (USCIS) to lawful permanent residents. The card serves as proof of their status as a permanent resident in the United States.

For example, if someone from another country comes to the United States and is granted permanent residency, they will receive an Alien Registration Card. This card will have their name, photo, and other identifying information on it. They will need to carry this card with them at all times to prove their legal status in the United States.

Another example is if a permanent resident needs to travel outside of the United States, they will need to present their Alien Registration Card when they return to the country. This card is an important document that allows them to live and work in the United States permanently.