Polyamory refers to the lifestyle of having more than one mate, as opposed to monogamy. However, those who consider themselves polyamorous are capable of having monogamous relationships of just one partner.
Polyamorous relationships can take a variety of forms. The relationships are not necessarily all sexual; they can also be purely spiritual, loving, or intimate in some other manner. Similarly, not all members of a polyamorous relationship are necessarily involved with all other members; for example, while someone may have two mates, the two mates may not be involved with each other (a "V"). In a polyfi relationship where all those involved have a similar bond and trust level with all the others in the relationship, and sexual activity outside of this group is rarely considered acceptable.
A "poly fur" is a polyamorous furry. Polyamory and open relationships seem to be common among those in the furry community, perhaps in part due to the prevalance of long-distance relationships or online relationships. Another element may be analogies with other animals, such as wolf packs or lion prides.