An identity can affect you in very many ways. And if you don’t have a good identity then you could end up with a rough life when you grow up. Your identity is what group you fit into and how you act in that group. What you do and how you do it.
For instance look at the book The Outsiders, the greasers and socs gave each other identities that they didn’t like each other. The reason the greasers gave the socs this identity was because the only time that they saw the socs was when they were drunk and looking for a fight. That socs gave the greasers a bad identity also