Swingers

I recently met a couple that... No, wait, I know a couple and I recently found out that they are "swingers". I mean they said they weren't "real" swingers, but I'm not sure what the difference between real and fake is. From what they told me, I would say they were swingers. But then, what do I really know about swingers?
I looked up the definition on merriam webster and definition b is " one who engages freely in sex", but that's not what i'm really talking about. Then I went to good ol' urban dictionary. The first definition was about the same 1. a person who dates/sleeps with multiple people at the same time.
But the second definition was more of what I was associating with the word:
2. A married person who enjoys swapping spouses with another married couple.
When the girl told me that she liked girls, the first thing I was worried about was that she didn't love her man. She quickly clarified that she loved him, but in addition she likes girls. And he enjoyed her "being" with women. Now two guys watching their wives/girlfriends making out or having sex doesn't mean they are swingers, does it? I don't know. But that's not all they do. I mean I don't know the whole story because I was walking around talking to my other friends. Meanwhile, my fiance got an earful from each of them.
I think my fiance who likes them both very much (platonically), thinks they have plans for us to join. Thinks that maybe next time we hang out, they might try to convince us or something. It kind of makes me laugh because in my mind it's a TV/movie situation, something that wouldn't happen in real life. I guess it does happen.
Do you know any swingers, real or fake?