Personas are archetypes of users that are developed early in the design process to represent the target audience. They are developed by conducting user research, brainstorming archetypes, refining them based on research, and sharing them with the project team. This helps the team understand user needs and make design decisions to meet those needs. The document provides examples of personas for a student, working professional, and professor to illustrate how personas describe relevant details about the user's demographics, job, goals, and lifestyle. Developing personas helps avoid guesswork and ensures the team shares a common understanding of the target users.