How does jealousy affect a relationship?

Well, it could mean a person doesn't trust and that you aren't really friends, There is always the friends who joke around about being jealous, but they aren't that kind of jealous. I believe that jealous can lead to a broken friendship of even a relationship with a love, because it means that you don't know what you have and why should you be jealous of someone else, just from an outward appearance, but you don't know what is on the inside.