Top results for Google Search: What is a GEDCOM?
GEDCOM (an acronym for GEnealogical Data COMmunication), is the standard for exchanging data from one genealogy program to another.
See:
TURNING A GEDCOM INTO A WEBPAGE
If you don't know about Cyndi's List, or Eastman's, then you are in for a treat.
I can't stress enough that you should Bookmark BOTH forthwith. ;-D
***UPDATE - 8/18/08***
This GEDCOM Stuff inspired me to create a song, hee, hee! ;-D
***END UPDATE***