The umbrella for any relationship style where partners agree to romantic or sexual connections outside the couple, honestly and with consent.
ENM and CNM are two names for the same idea. "Ethical non-monogamy" is the community phrasing, carried into the mainstream by the 1997 book "The Ethical Slut" — the word "ethical" insisting that non-exclusive relationships could be principled rather than sordid. "Consensual non-monogamy" is the phrasing academic researchers settled on, because "consensual" states the actual mechanism (everyone agreed) without asking anyone to referee what counts as ethical. Same tent, two entrances.
The most common misconception is that this is just a polite word for cheating, or a synonym for polyamory. It's neither. The whole point is the opposite of cheating: cheating breaks an agreement, ENM/CNM is the agreement. And polyamory is only one room inside it — the umbrella also covers open relationships, swinging, relationship anarchy, and plenty of arrangements people build without a label. What they share is not a structure but a starting condition: informed consent, out loud, in advance.
In practice it shows up less as a lifestyle and more as a set of ongoing conversations — about boundaries, safer sex, jealousy, time, and what each person actually wants. It is not automatically more evolved than monogamy and not automatically messier; it is just honest about a negotiation that every relationship runs, whether or not it says so.