How does a poly relationship works?

I am genuinely curious, okay? And I hope I'm not offending anyone, because that was definitely not the intent; I just don't understand the concept. Like, three people love each other. Yeah, but the more I think about it, the more confusing it gets. Like, in a group of three, even from personal experience, don't we tend to like either one more than another? Not to mention, love is a heavy emotion to feel towardstwo people, at the same intensity, so I have no personal experience there(maybe that's why I can't understand)I mean, I can't imagine how it works. Doesn't the relationship fall apart because one feels isolated? Or something similar?