I've talked about mission and vision statements, but I haven't talked about charters. You'll hear charters talked about in two contexts, team and project. Personally, I don't believe in team (or org in general) charters. Those are mission and vision statements.
To me, a charter has an end goal (just like a vision), but when the end goal is reached the project is over and work stops. Yes, a project can evolve and where you end up isn't always where you thought you were going, but there is an expected end. A charter is both more and less than a vision and mission.
It's less than that in that its scope is in some ways smaller. Not only does it have an end, projects and their charters exist within a larger organization. Self-driving cars that drive more than themselves is a vision. PLT is a project and has a charter.
A charter is also more. Besides having an end state (vision) projects also have roles and responsibilities defined. Who's involved? Who's responsible for what? Who are the pigs and chickens? What are the processes the project will use? Some of these need to be written down, others are assumed/inherited from the org.
Regardless of whether all of those things (and others) are explicitly written down or not, you've got them. The benefit of having them written down and agreed to is that whenever there's a question you can refer back to the doc and get clarification.