Ethical Non-Monogamy (ENM) is more than just being able to have sex with multiple partners. Yes some people have sex with multiple partners, others may just have emotional relations and support outside their primary relationship. How those in the relationship set up their rules is up to them. ENM is generally broken down into three main forms:
Polyamory is loving multiple people at one time. This can be further broken down to various sub categories such as being in a triad, a trouple, a quad, or any number of extra partners. This is generally referred to people who are in long committed relationships with multiple people.
Open relationship is a very broad term but generally refers to relationships where they agree to see other people. Usually, those in the relationship establish some ground rules on what they can do with others and when.
Swinging is a form of social sex. This is where people either solo or as the couple engage in various sex acts with others. It is best if everyone involved discusses and agrees on guidelines before hand. As with all forms of ENM, open and honest communication is best.
If your are in an ENM relationship (either as a long term thing, or as an experimental night) and have relationship issues you need to address, as a Marriage and Family Therapist, I may be able to help.
If you are curious about ENM, but fear how your partner may react, I may be able to help. (This lifestyle is not for everyone. In many ways, it takes more honesty, communication and trust than a traditional relationship.)