Under U.S. immigration law, two (2) main visa categories exist: nonimmigrant and immigrant.
Nonimmigrant visas are generally temporary with finite periods of validity. Some nonimmigrant visas require the bearer to intend to return to his/her home country at the conclusion of his/her stay in the U.S. Most employment-based nonimmigrant visas are employer-specific. Some are also job- and location-specific.
On the other hand, an immigrant visa allows the bearer to enter the U.S. and live and work here permanently. As evidence of permanent residence, the USCIS issues permanent resident cards (”green cards”).