Understanding Roles & Grant Options

I've been reading the documentation and I'm trying to understand what
'GRANT' options make up a 'superuser' in PostgreSQL.

I've got my account which is 'carlos' and then I have an account
called 'jason'. Can someone please explain the difference between the
two roles:

postgres=# \dg
List of roles
Role name | Attributes | Member of
-----------+--------------+-----------
carlos | Superuser | {it}
it | Cannot login | {}
jason | Create role | {it}
: Create DB
postgres | Superuser | {}
: Create role
: Create DB

Obviously 'Carlos' is a superuser but what does that exactly entail
beyond CREATEDB & CREATEROLE?

http://www.postgresql.org/docs/8.1/static/app-createuser.html