No idea if this is a question fitting to this blog but I've been trying to inform myself about polyamory to be more open and in all the examples I found online or in books it's always just one person being in love with two or more people, and everyone is fine with it. My question is, what if all three or more people are in love with each other, like everyone is in love with everyone in the relationship, would that still be polyamory? I just don't want to offend anyone by using the wrong term.
Yes, that is definitely still considered polyamory! That is often referred to as a "triad" if there are 3 people involved, or "polyfidelity" if all 3+ people are only involved with each other. Keep reading and researching - you'll find plenty of examples of what you're describing.