Different to having an open relationship or polygamy, polyamory is similar but is where one's other partners have knowledge of each others' other partners. In some cases one's other partners are in polyamorous relationships with one another respectively.
Mostly something practiced in all it's supposed glory by the young, hip and willfully alternative, it is something which doesn't lend itself to conventional notions of love and belonging. Partnerships built on such a dynamic are plagued with jealousy and insecurity and don't often last, with many who might have once partook in polyamory ending up in more conventional relationships or couplings- by comparison.
Polyamory has its sub-genres (for want of a better word). Polygamy, being the practice of having multiple wedded partners is mostly done so out of religious or traditional purposes. Utterly unnecessary in my point of view- and usually proves to serve the male involved more than his wives. In some cases of polygamy polyamory is also practiced in terms of sexual relationships, not necessarily in a marriage context.
What's the likelihood of polyamory being workable in the real world? Polyamory may certainly have its virtues, for example it can teach people the difference between love and ownership, loving a person and loving love, however for the most part the benefits and workability of polyamory is short-term. It's a great exploration but, maybe, is something which goes against the natural urge to mate and nest.
Bisexual polyamory is also a thing. Very unique and probably more workable in my opinion if all parties are bisexual.
I think it's fairly safe to say that if you are wanting to open your relationship up to (or seek out) polyamory you have to be a very open minded person and be able to temper your emotional attachment. Be open minded to all potential outcomes. Also be open hearted, not just to the notion of multiple lovers or partners but to each of them individually so as to be able to recognise when one may be feeling anything less than complete in the acceptance of the scenario. Furthermore, have this ability to reflect on these feelings yourself to save you and everyone a lot of hassle by, if you are of such a mind, not staying at the party too long and leaving on good grounds.
That's perhaps the real risk of polyamory, is inadvertantly and likely, unavoidably hurting someone you care for, as such, be careful.