Roles and Users

[Privileges] -> [Role] -> [User]

Privileges gives permission to access database objects.

A PostgreSQL database by default has public schema
Access to public schema granted by public role by default.
User and Role can be used interchangeably.
But User is a Role can login.
(Access) Privileges: SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER, CREATE, CONNECT, TEMPORARY (or TEMP), EXECUTE, USAGE. There is ALL PRIVILEGES.
PUBLIC key word indicates the privileges are to be granted to all roles
Commands: GRANT

CREATE ROLE user WITH LOGIN PASSWORD 'secret';

-- Schema names you have access
show search_path;

\duS pg_*

Read-only user