Belleisle, I understand first getting on the forums and not quite knowing where to start.
In my opinion, the man you described does seem to be having affairs with multiple women, which is not considered polyamory. One could call it swinging, although in either poly or swinging, one's partners are still aware of any sexual activity or relationships. That is what makes it "ethical" non-monogamy.
You indicate that he claims to care about his sex partners, but apparently not the wife he chose to build a life with, and I find that very sad.
People may define polyamory in sorts of ways, but I've learned that honesty and trust are the foundations of any relationship, including polyamorous ones.
The suggestion to look for posts and threads is a good one. Enter in a keyword and see what you can find.
And please don't be afraid to ask questions. You are not required to do a lot of research before proving to anyone that your question is worthy. Yes, it may have been asked many, many times before, but it's still a new question to you. Take care!
Neon: Some of us may be confident enough to know the textbook definition of what polyamory is, but many people are unsure, which is what leads them to these forums. I'm not a custodian, just a member. I look at my presence on the forums as a way to seek out the information and support I need. I also hope to share any experience and opinion I have, so that I may help others.
I'm a retail manager and if a customer came in looking for something I thought was obvious, I wouldn't say "Gawd, didn't you SEE the giant sign there?!" I would try to be polite, welcoming, and do my best to help without judging their level of understanding. Your response came off as rather harsh and not especially welcoming to a new member who is obviously unsure and seeking help. Whether or not she is asking on someone else's behalf is irrelevant. She's asking. Maybe you are fortunate enough to be a part of a community or communities that fully understand what polyamory is, but most of us aren't. When someone wants to understand what polyamory is, for themselves, for someone else, or just for the sake of knowing, it's in our best interest to articulate our answers responsibly.