Your Kik display name is different from you kik username. Well in concept - your kik username and your display name can actually be the same, but most likely they are different and serve different purposes.
Your Kik Username
Kik usernames are the usernames that are given out by others. The Kik app recognizes these usernames and identifys your profile using it. As opposed to some apps like WhatsApp where you're required to share your phone number, Kik does not require that you share your phone number when chatting with others. This makes the experience of meeting new people online much better.
Your kik username must be unique and cannot be duplicated. This cannot be changed later and your kik username can never be registered again. If you lose access to your account or it becomes inactive, then you must choose a different username. Although it sucks that you lose your username, nobody can pretend to be you if your username is deleted.
Your Kik Display Name
Your kik display name is the one shown to others in chat. Since it is difficult to get a unique username online, having the ability to pick your display name is a nice feature to have.
Your kik display name can be the same as somebody elses. This works because Kik, as we have said, uses kik usernames to identify users. The display name for Kik, unlike the kik username can be changed.