a tar.gz file is comparable to a zip file.
the tar part is used to group all of the original files into one "tar" file
the gz part is to apply compression to the files.
to extract this kind of archive you need to do the following...
tar xvzf FILENAME
and read the README file that is found inside so you can find out what to do next.
(make sure you search for answers for your questions before you post. I answered this same question two days ago.