The people who back-bit about you, are not considered as friends. This is very common among young aged group, and especially among friends. People usually feel bad about not having something the other person has. As we all know, nobody is perfect. Someone is beautiful but not intelligent, while someone is not beautiful but is very good at studies. At times people envy those who are popular too.
People feel jealous about your looks, the way you carry yourself, the way people admire you. These are the most common reasons of feeling jealous and when they feel jealous they feel insecure and they talk behind your back and try and turn other people against you. They make fake stories, and tell other people bad things about you. At times people do agree to what they are saying, misunderstandings are created.
People who do such stuff are basically frustrated from their life and they feel jealous from other people’s success or their happiness since they don’t have happiness in their life they don’t want others to be happy too. So with such people all you can do is just ignore them, let them say what ever they want to. You know who you are and what you are, you don’t need to explain yourself to the others. And you’ll see they won’t do that any long.