Polyamory is a relationship style that involves an openness to be being involved with more than one person at the same time. Polyamory is about responsible non-monogamy. Polyamory is not about cheating, or dishonesty. Polyamory pre-supposes that all people involved consent to this arrangement, and are honest about what is going on.
There is a major distinction to be made between what is called "Swinging" and Polyamory. In swinging, the intent is to engage in non-monogamous sexual behavior without the development of love, affection or personal intimacy between oneself and the secondary partners. Swingers generally seek to engage in recreational sex without emotional intimacy. With polyamory, there is no such restriction, and the intent IS to allow such emotional intimacy to exist, develop, and grow between the people involved.