Ethical non-monogamy is an umbrella term for any kind of honest, open non-monogamy that includes the knowledge and consent of all the people involved. It describes many types of relationships, from polyamory to swinging to "open marriages" that allow the members of a couple to have recreational sex on the side.

Polyamory is a specific type of ethical non-monogamy, in which people have more than one romantic relationship at the same time. These romantic relationships may or may not involve living together, but there is an understanding that the sex is not necessarily just recreational; there is a focusing on multidimensional, loving, intimate relationships.

Of course, polyamory is not exclusive of other forms of ethical non-monogamy. People can, for example, have more than one romantic relationship and also have casual relationships as well.

The key element of all ethical non-monogamy is honesty. Nobody is sneaking around behind anyone else's back. All the people involved in a non-monogamous relationship are on board with it.

This means, for example, polyamory is not cheating. Nor does it mean dating a lot of people casually without telling any of them that you're dating someone else.