Foreign Keys, Triggers and such

I am a MIS student at the University of Georgia.  I am doing a project
for my Systems Analysis and Design class, and I am using PostgreSQL for
the Database.  I have taken a data management class and we always used
foreign keys.  I used a win32 program written by Power Soft called Data
Architect.  I used the PostgreSQL odbc drivers to interface with the
linux box with the database on it.  The reason I am writing all this, is
that it created all the tables, indexes, and sequences just fine, but it
skipped over the foreign keys.  I understand that a trigger can be used
instead of a foreign key, and I have read an explanation for this reason
at
http://www.mysql.org/Manual_chapter/manual_Compatibility.html#Missing_Foreign_Keys

I was wondering if this is the same reason that PostgreSQL doesn't use
foreign keys, and I was wondering exactly how to use the triggers
instead of the foreign keys.  Sorry for a long story in my message.
Thanks in advance for the help.
Daniel Spratlen
spratlen@arches.uga.edu