Does the 'PURGE' method in HTTP only removes the object from cache memory?

I have searched for purge method but didn't found anything precise.

A purge is what happens when you pick out an object from the cache and discard it along with its variants. Usually a purge is invoked through HTTP with the method PURGE. An HTTP purge is similar to an HTTP GET request, except that the method is PURGE.

This is what I found.