Polyamory is a lifestyle in which you can choose to have more than one romantic partner in an ethical way. This is not cheating--all those involved know the situation and approve of it. The important point is that polyamory is a lifestyle (or lovestyle) that is based on ethical non-monogamy.
Many who are new to ethical non-monogamy or who are not accepting of non-monogamous lifestyles often confuse polyamory with swinging. Polyamory and swinging, when practiced in an open and honest fashion are both forms of ethical non-monogamy. However, each fills different needs.
Polyamory places the emphasis on committed romantic attachments. Sexual adventure is secondary to love. Many swingers, however, tend to avoid romantic attachments and put the emphasis on sexual "play".
Some people who practice polyamory start out swinging and then find that romantic love is more fulfilling. Some cross back and forth between polyamory and swinging. The two lifestyles are different ends on a spectrum of ethically non-monogamous lifestyles.
This site is oriented towards the polyamory end of the spectrum but everyone wishing to learn more about polyamory is welcome here regardless of their orientation or interests.
Within polyamory, there are as many types of relationships as there are people. Some choose to have a polyfidelous relationship, where they are faithful within their "family" of partners and consider themselves to be married to multiple people. They may jointly own houses and raise children together. Other polys live openly, preferring to be free from committment. There are many relationships that fall somewhere in between. It is up to the individuals involved to determine their own relationship model.
Where can I find out more about Poly?