Application for Permanent Employment Certification (PERM).#Labor market test. #US workers.
An application for PERM is a test of the labor market. This test of the labor market must be completed in accordance with instructions specifically detailed by Dept. of Labor regulations. There are some employment visa categories where the person can self-petition. This will not work for labor certifications. For example, a foreign national, as President/Owner of a company is not going to test the labor market for a company President position and give a U.S. worker his job. This is the best way I can explain "a position is not truly open to U.S. workers. . ."
The Department of Labor website has its own explanation and a lot of information regarding the labor certification process as well.
Note that the reasons why your PERM can be denied are a moving target and may catch you by surprise.