well it depends. If you're talking freelance makeup artist in general it's an artist who works for themself. They don't belong to another company, they dont have a boss that they report to, they're a self employed artist.
If you're talking say a freelance artist for MAC, they're "on call" employees. They are employed by MAC, and they're paid by MAC, but they aren't entitled to the full benefits of a full, permanent MAC employee. They only work as like subs when people call in, or on days where counters/stores get unexpectedly busy, during busy seasons like Mother's Day and Christmastime, and they work special events i.e., NocturnElle Unveiling events. And they don't belong to one particular store or counter, they can be called by any store or counter in a particular region.