'now - 4 hours ago' ?

I'm still learning SQL. :-)

Now I have upgraded my PostgreSQL database to v6.3.2, and have the
following table.

CREATE TABLE testdate(
received timestamp DEFAULT CURRENT_DATE,
info text NOT NULL
);

I want to select the info received (inserted) more then 4 hours ago.
How do I specify that in SQL? Is timestamp the best datatype for this
kind of query? Which date-types exists in PostgreSQL, and what is the
difference between them. I'll be very happy to get pointers to good
intros. :-)

I'm not on this list, so please send copies to me.
--
##> Petter Reinholdtsen <## | pere(at)td(dot)org(dot)uit(dot)no
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