Swingers are often stereotyped as having lascivious affairs, but depending on what you consider cheating, almost everyone is having some type of affair.
For me, an affair isn't necessarily a physical relationship; it can be an emotional connection as well. Depending on who you are, either connection can constitute an affair.
By this definition I have both emotional and physical affairs. I'm not in love with these people; some are friends that I share a side of myself with that I don't share with everyone. Others I just have sex with and don't care if I ever see again.