To understand how this works you have to picture three different "entities" talking to each other: your browser, the OpenERP server and the database server.

When you start up OpenERP, before any users connect, it needs to be able to get into the database server and load up the list of all available databases. So, OpenERP needs its own password.

When the OpenERP administrator creates or drops databases, he/she needs a password that is NOT known by the many possible administrators of individual databases.

When an administrator uses a browser to connect to the OpenERP server, the first step is to choose a single database for use. Each database is managed separately, and possibly by different administrators. The user can only gain administrative access to the databases for which he/she knows the specific admin password.

In other words, you actually have three passwords:

1. The password OpenERP uses to get into PostgreSQL. It is known as "db_password" in the OpenERP configuration file.
2. The password the site administrator uses to control all the databases; the Master password. It is known as "admin_password" in the OpenERP configuration file.
3. The password an individual database administrator needs to have full control over a single database; the Admin password. This is stored, along with all the other database users, inside the database itself.

Caveat : This is true of 6.1 (and just about every 3-tier system I've ever seen), it MAY have changed for 7.0, but I'll leave it to someone else to slap me down if I'm wrong.

To see an Admin password you can follow these steps (tried in 6.1):

you:-$ # Take on postgres user privileges
you:-$ sudo -sHu postgres
postgres:-$ # Start up the PostgreSQL command line.
postgres:-$ psql -d yourDataBaseName
psql (9.1.7)
Type "help" for help.

yourDataBaseName=: # Query the user table
yourDataBaseName=: select login, password from res_users;
 login | password 
-------+----------
 rick  | rick123
 admin | WheyHaarD4u2Guess
(2 rows)

yourDataBaseName=: