Each user is given a role for their own personal use (commonly called a login or username) and a password they must use to gain access to the database. It is good form to change your password occasionally.[3]
The database can grant specific users (via each user's personal role, aka login) various levels of access to specific tables, although such access is not common as it is difficult to administer and maintain such a fine grained degree of control. For further information see the PostgreSQL documentation on Database Roles.
Rather than maintain database access privileges on a per-user basis it is more convenient to grant users additional roles, roles shared by many users, and then grant these roles different levels of database access.
Gombe-MI contains the following (shared) roles:
The members of this shared role have read access to Gombe-MI data but cannot add, delete, or otherwise alter any of the data.
The members of this shared role have unlimited rights to the Gombe-MI data. They may add data, delete data, or alter existing data. They may not, however, alter the structure of the gombemi database or change the rules to which the data are required to conform. Thus, they may not add or delete tables, alter triggers, or write or replace stored procedures.
[3] That way if you unwittingly revealed your password last weekend, after that fourth bottle of wine you just knew was a mistake, by the time everybody sobers up the password will have been changed and the amount of damage done is limited.