export everything to text file

Hi,
   Newbie question here:

   I had an sys admin recommend that I export my critical DB's to
a text file before the tape does it's auto backup (dump)
That way I don't have to stop the PostgreSQL each night for 30 mins.

What is this called.  What might it be called in the index of a book like:
PostgreSQL Essential Reference
or
Beginning DB with PostgreSQL

Or how about an URL for a HowTo..

TIA

- Jim