class as a table column?

[libpq++ with gcc egcs-2.91.66 (egcs-1.1.2 release) on RH linux 5.1
with Postgres 6.5.]

I've seen in the manual that one can create a table with a class/table
as one of the columns, e.g.:

--set (complex) attribute may be of the same type as the
--relation being defined (as here) or of a different complex
--type. The type must exist in the "pg_type" catalog or be
--the one currently being defined.
--
create table newemp (name text, manager newemp)

and I have been able to do this in psql.

But what does this really mean? And how does one insert or extract
data from such a column? And what is it good for? It seems like
maybe a powerful facility, but I really don't understand it.

Is this sort-of the same as inheriting from that class?
Does anyone have examples of its use?

Thanks,
George

George Young, Rm. L-204 gry(at)ll(dot)mit(dot)edu
MIT Lincoln Laboratory
244 Wood St.
Lexington, Massachusetts 02420-9108 (781) 981-2756