What do you mean by "internal security" and "external security" in security?

Now, according to the regulations, only those who have obtained the security qualification certificate through the professional training of security companies are called security guards. General security guards are hired by units from regular security companies with higher prices. Considering the cost, the position of recruiting employees in some units is not particularly important, or it is the facade of the company. These recruits are called internal insurance, and those recruited from security companies are called external insurance. Of course, this is just a common term in the current society.