For family preference and employment based visa petitions, a priority date (PD) is the filing date of the I-130 or I-140. Once the PD becomes "current" on the Visa Bulletin (issued monthly by the State Department) for the category and country, THEN a visa is available. Once a visa becomes available, you can file for either an Immigrant Visa if abroad (the Consulate contatcs you) OR you can file for adjustment of status on an I-485 with USCIS inside the U.S. (nobody contacts you), IF eligible (in legal nonimmigrant status). PD's don't apply to Immediate Relatives of USC's.
What immigrant category, what country and when was the petition filed?