PolyOz

Is Polyamory "about sex."? Yes and no. For most Polyamorists, the core attraction is "amor" or "amour" -- love, albeit romantic/erotic love. Mostly the focus is on relationships. However, this definitely can involve sex as well, and it's that aspect which distinguishes polyamory from monogamous couples with close platonic friendships.

Another variant or modification to monogamy, involving sexual exploration in an environment structured to contain it without damage to an otherwise monogamous relationship. Like polyamory, it involves honesty and consent. Unlike polyamory it typically tries to stringently avoid love, romance or relationships outside the existing pair (though friendships are OK), and is engaged in mainly by couples (though some groups allow single women as well; rarely are single men allowed). Lifestyles is another term used for this option.

The swinging subculture is generally very different from poly subculture, and almost nobody could fail to notice the difference in conferences, gatherings, parties, magazines, email groups or other manifestations of the two movements. Nevertheless, a few people are involved in both movements, or tend to operate in a grey area "in the middle". Human lives and hearts don't always fit neatly into a set of mutually exclusive boxes.

Less commonly used. While many people have fairly consistent ideas of the difference between primary (or nesting) relationships and secondary (or non-nesting) ones, the distinction between secondary and tertiary is often more subtle and more idiosyncratic (for those who even use the term). You have to ask what distinction any individual makes, to understand "tertiary".

A somewhat less common usage for primary, secondary and tertiary is for simple ranking. The most involved partner is primary by definition, the less involved is secondary, etc. In this usage, one cannot have two primaries, or a secondary with no primary. Some poly folk tend to avoid these terms entirely because to them it implies a ranking they do not want to endorse, or do not identify with.

A triad is a three way relationship, typically referring to a primary relationship

Three way relationships may be fairly symmetric with all three pairs being fairly equally involved (a triangle); or two of the pairs may be substantially more bonded than the third pair (a vee or V, think of the letter V). These are terms for the ends of a continuum, not binary alternatives. Also, some triads may describe themselves differently in regards to emotional connections and sexual ones, so it's quite possible for example to have a sexual Vee with an emotional triangle.

Three way relationships may be fairly symmetric with all three pairs being fairly equally involved (a triangle); or two of the pairs may be substantially more bonded than the third pair (a vee or V, think of the letter V). These are terms for the ends of a continuum, not binary alternatives. Also, some triads may describe themselves differently in regards to emotional connections and sexual ones, so it's quite possible for example to have a sexual Vee with an emotional triangle.