Also known as a “tarball,” the preferred file format here is the “.tar” file format. It is an archiving format with no data compression. That means your already compressed “.jpg” images do not receive another round of pixelation.
But overall, few people care about that; the chewy center is what we are after. Here is the low-down:
Modern distributions will allow you to use a program such as Archive Manager (File Roller) to double-click on an archive name and extract it, provided the file names have been left the same.
Alternatively, use the command:
tar -xvvf filename.tar
If a file is split in parts (YYZ.tar.000, YYZ.tar.001, etc.) then running the command on the first file in the series should work.
The 7-Zip application will take care of all your extraction and compression needs. You can find it here: http://www.7-zip.org/