The term “Adjustment of Status” refers to an immigration application that is processed entirely within the United States, through a USCIS office. In order to file an Adjustment of Status application, the applicant must have entered the United States legally and have a visa waiting for them.
For employment based immigration applications
If the applicant is outside the U.S. with an immigrant petition (Form I-130 or I-140) approved and discovered that the priority date is “current” and a visa number has become available. The applicant attends an immigrant visa interview at a U.S. consulate or embassy in the applicant’s home country.
Generally speaking,it is normally more difficult to enter the U.S. while an immigrant visa petition is pending. The applicant may try to apply for a non-immigrant visa such as B1/B2, but the applicant needs to provide evidence of the non-immigrant intent with the pending immigrant visa.