Only roles that have the LOGIN attribute can be used as the initial role name for a database connection. A role with the LOGIN attribute can be considered the same thing as a "database user". To create a role with login privilege, use either

CREATE ROLE name LOGIN;
CREATE USER name;

(CREATE USER is equivalent to CREATE ROLE except that CREATE USER assumes LOGIN by default, while CREATE ROLE does not.)

A database superuser bypasses all permission checks. This is a dangerous privilege and should not be used carelessly; it is best to do most of your work as a role that is not a superuser. To create a new database superuser, use CREATE ROLE name SUPERUSER. You must do this as a role that is already a superuser.

A role must be explicitly given permission to create databases (except for superusers, since those bypass all permission checks). To create such a role, use CREATE ROLE name CREATEDB.

A role must be explicitly given permission to create more roles (except for superusers, since those bypass all permission checks). To create such a role, use CREATE ROLE name CREATEROLE. A role with CREATEROLE privilege can alter and drop other roles, too, as well as grant or revoke membership in them. However, to create, alter, drop, or change membership of a superuser role, superuser status is required; CREATEROLE is not sufficient for that.

A password is only significant if the client authentication method requires the user to supply a password when connecting to the database. The password, md5, and crypt authentication methods make use of passwords. Database passwords are separate from operating system passwords. Specify a password upon role creation with CREATE ROLE name PASSWORD 'string'.