A persona is a short description of a typical kind of person a product is meant to help. It may include what that person is trying to do, what they already know, and what gets in their way.
For example, a team making a beginner coding tool might keep in mind a learner who has never opened a command line. This helps the team make clearer choices. A persona is a useful summary based on research, not a real individual or a substitute for listening to actual users.