The fiancé(e) visa, also known as the K-1 nonimmigrant visa) allows your fiancé(e) to enter the U.S. for 90 days to get married. Once your marriage takes place, your spouse may apply for permanent residence and stay in the U.S. while USCIS processes the application.
To be eligible, you (the petitioner) must be a U.S. citizen, you must marry your fiancé(e) within 90 days of entry, any previous marriages must have been legally terminated, and you must have met your spouse at least once within 2 years of filing your petition (with exceptions).
If your fiancé(e) has a child under 21 and unmarried, a K-2 nonimmigrant visa may also be available. After admission of your fiancé(e), he or she may immediately apply for permission to work by filing an application for employment.