An open relationship is an interpersonal relationship in which the parties want to be together but agree to a form of a non-monogamous relationship. This means that they agree that a romantic or sexual relationship with another person is accepted, permitted, or tolerated. Every operelationship is different because what exactly the relationship entails is defined by the wishes and desires of the parties involved. Some may only allow flirting, whereas others may permit dates, kissing, or sexual acts. By combining most common definitions, the overarching theme is that an open relationship is when the parties involved have two or more romantic or sexual relationships occurring at the same time either as a short term, such as dating, or long term, such as open marriage. Because of an open relationship’s structure, it is flexible enough to allow constant change. With this in mind, the relationship between one and his/her partner is always being renegotiated so that the relationship may grow.
With this, I can't imagine being in one myself.