.tgz

.tgz, also known as .tar.gz or a "tarball", is a common method for compressing and archiving a folder. The name comes from two seperate processes: the archiving part, where the folder(s) are placed into a single .tar file; and the compression part, where the tar file is compressed to a smaller size using gzip.

Unpacking
A tarball can usually be unpacked via the command line with:

Graphical frontends, such as Ark can also extract it.