you need this kind of explanation - Mailing list pgsql-docs

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Page: https://www.postgresql.org/docs/10/static/index.html
Description:

right off the bat, you should have this kind of explanation up there in
chapter 1:

https://www.liquidweb.com/kb/what-is-the-default-password-for-postgresql/

this will orient any noobs immediately.

also, the word "role" and "user" should not be used interchangebly. they
mean different things.