bz2 is a more compact version of the gz file.
you're going to want to go to the directory where the tarball is: in the terminal and enter in:
tar -xzvf filename.tar.gz OR tar -jxvf
then it will extract and create a directory within the current one
change into that directory
now this is where you must read the README, u can get at it through this command vi README or you can just access it through your Xwindows and jut click on the tarball
usualy now you will run ./configure
followed by make
and then make install
some programs will sub out the ./configure for something like ./mozilla-installer (thats in the case of mozilla
hope this helps