What is Adjustment of Status?

The normal path for aliens to enter the United States with a legal permanent resident status is through a petition filed by their family or by a petition or sponsorship filed by an employer. This is called consular processing and the alien applies while he or she is still in his home country. The alien migrates to the US only after the issuance of an immigrant visa and enters the US after being admitted.

An Adjustment of Status is a request or petition by an alien holding a non-immigrant visa for the issuance of a legal permanent resident status or green card. This means that the alien has entered the US legally and was admitted under a valid non-immigrant visa. But during his or her stay, the alien acquired a legal basis for applying for a green card or a legal permanent residency status. The alien may apply for a green card without leaving the US to go back to their home country and processing their visa there.
Aliens who are in the US under a non-immigrant visa can apply for an adjustment of their status from a temporary US resident to a permanent resident when they become eligible to apply for legal permanent residency under either a humanitarian basis or under one of the special immigration status such as when they are granted asylum or refugee status, or when their family files a petition for the issuance of a green card to them.
Filing the request or petition for adjustment of status is the first step in the immigration process. It is followed by checking on the availability of a visa, of going to an interview and providing biometrics (fingerprints, etc.) before the decision on the petition will be sent to the immigrant.