Punjabi and Muslims are two different terms that can be used to describe people. There are times when this can be used to describe the same person. When you say that a person is Punjabi, this means that the person lives in Punjab which is one of the places that you will find in India. “Muslim” will refer to the type of religion that a person may have.
The same way that there are some people who can be described as “Christians” or “Catholics.” It is likely that a person can be a Punjabi and a Muslim. Yet, there are also times when they do not necessarily have to go together in order to describe the same person.