Adjustment of status (AOS) refers to the process by which an individual petitions USCIS to change his or her status from nonimmigrant to immigrant (i.e., to become a lawful permanent resident and receive a green card). It can only be filed by an alien in the United States. While the AOS petition is filed on Form I-485, the timing of its filing and the supporting documents sent therewith can be quite different depending on the underlying basis for the adjustment petition (e.g., family based, employment based, etc.).
Most AOS petitions require an interview at a local USCIS Field Office, as well as an extensive background check. Processing times can vary widely.