We use a "people" document. It lists our names, contact information, roles, responsibilities, etc.
We use a "pitch" document. It summarizes the project and its progress, much like a startup pitch deck.
We use an "onboard" document. It explains how to join our team, how to set up, and how to collaborate.
We use a "wordbook" document that explains terminology, a.k.a. a glossary, dictionary, abbreviation guide.
We use a "responsibilities" document that explains who is responsible for what, such as a Responsibility Assignment Matrix (RAM) or a RACIO matrix (Responsible, Accountable, Consultable, Informable, Omittable).
We use a "canvas" document that is our Business Model Canvas.