"FWB" is a text and social media acronym that means friends with benefits. It is most often used by teens and single adults who do not want to become involved in a monogamous and committed relationship.
A friends with benefits relationship involves two people who are physically attracted to one another. They spend time together sexually but are not considered to be in a serious relationship or even casually dating. Friends with benefits do not typical participate in general dating practices, such as exchanging Valentine's Day gifts or meeting each other's parents. This type of arrangement seldom evolves into a committed or serious relationship.