What is a Tarball?
A tarball is quite similar to a zip file in windows. There are a number of programs you can use to open tarballs, here are the most common:
Info from Mikma on the Ace forums:
Here's some info how to extract them on Macintosh: http://www.versiontracker.com/dyn/moreinfo/macosx/182 or open Finder ->Applications -> Utilities -> Terminal: tar zxvf filename.tar.gz
You can find more info on tarballs on Wikipedia