The easiest and simplest way to know the difference between swinger clubs and socials, groups or Meet-n-Greets is that swinger clubs are usually a brick and mortar physical locations where you meet other swingers.
Socials, groups, and Meet-and-Greets may often meet in the same location but it is often either a residence or some space that they have secured to meet.
A similar type of club is a masturbation club in which members, either single-gender or mixed, masturbate together in public or private rooms.
Sexual intercourse is generally prohibited in such clubs.
Larger establishments may include the facilities of an ordinary nightclub such as a bar and a dance floor.