A user persona compresses what a team has learned from research into a single representative profile that guides product and marketing choices. A useful persona names the role, the job to be done, the alternatives the user is currently using, and the success criteria they'd use to evaluate a new tool.
Personas are often confused with ICPs. The ICP describes the buying organization (industry, size, motion); the persona describes the human inside that organization who actually feels the pain. Most B2B teams need both.