The DOL, in concert with the local State Workforce Agency (SWA), processes applications for Alien Employment Certification (Form ETA 750). The date the labor certification application is filed with the SWA is known as the priority date. After the labor certification application is approved by the DOL, it should be submitted to the CIS service center with an I-140, Immigrant Petition for Alien Worker.

http://www.ows.doleta.gov/foreign/perm.asp#proc