An interesting definition I came across on the internet...

Couple to couple sex-Swinging or swinger- sometimes referred to as the swinging lifestyle or simply The Lifestyle, is "non-monogamous sexual activity treated much like any other social swinger activity, that can be experienced as a couple engaging for sex is the most common sexual practice in the swinging community.

It is commonly refer to the heart and soul of the swinging lifestyle although this simplified term is also used by people into Leather and BDSM.

Many swinging couple will swap partners back and forth during sex play in the same room and same bed, while others may swap partners for sex in separate rooms and beds.

There are no “right or wrong” ways of going about having couple to couple sex play. It is all about what you, your partner and swinging partners decide and want at the time.

Certainly there are no certain rules to follow by any couples, instead rules are usually formed and followed by individual couples themselves.