Online Backup

Dear All--

I'm investigating PostgreSQL for a web-based dB project, and have been
unable to find any documentation about its abilities to perform backups
while online.

The Features Comparison table on the postgresql.org site lists this as a
feature of 6.2.1, but that's about the only reference to the procedure I
can find.

How easy is it to back up a (running/online) PostgreSQL dabatase? Is it as
simple as copy/tar, or is there some inbuilt database replication system?

I'm hoping to be able to use PostgreSQL because I believe very strongly in
open code development projects, but I have to convince my management that
it makes strategic sense and issues like backup/recovery are naturally
critical to that. Thanks very much for any information you're able to provide.

CYa,
JEREMY