Those that are in a mutual and often platonic friendship where sex might be incorporated but is not based on the necessity or expectation of sex. A situation in where sex occurs because of a friendship, not a relationship that occurs because of sex. Not to be confused with Friends with Benefits, or screw buddies.
Friends with options could be two people who might have known each other years and while they care about each other, have no romantic feelings for each other. While there might be a mutual physical attraction, the sex is based on a certain level of trust and friendship. Marital or relationship status is not a concern, because the sex is often recreational more so than emotional. Even if it occurred only once, the friendship would remain intact (unless it was bad), but there is an understanding that it could happen again without expectation.