Users
Who is signed in, what they have configured, and how to look up other people in the directory.
Everything about identity once the sign-in is done. The Authentication section covers getting a session; these pages cover what you can read and write with one.
The current user
Who is signed in, their identities and administrative flags — and why results are already filtered by their rights.
User settings
Per-user preferences stored server-side, with a shape you extend yourself.
User profile
The business profile: job title, organisation, location, skills.
Passwords
Changing a password, and the forgotten-password flow.
Impersonation
Running requests as another user, and what it changes about signing out.
Finding principals
Search-as-you-type over users and groups, to assign owners and readers.