From MEPIS Documentation Wiki
Compression is the process of encoding information using fewer bits than the original representation would use. It is used for items ranging from individual files to entire Linux distributions--MEPIS was a pioneer, in fact, in using compression to make possible a LiveCD.
A number of graphical and CLI compression packages are installed by default with MEPIS. KDE's Ark is the default graphical program for managing various archive formats within the KDE environment. Archives can be viewed, extracted, created and modified from within Ark. The program can handle various formats such as tar, gzip, bzip2, zip, rar, and other formats if the appropriate backend CLI programs are installed.
Other applications can be installed through the repos in the usual manner.
Ark is most commonly used with the context menu: right-click on a compressed package to see the compression options. Most of the time the command "Extract Archive Here" accomplishes the user's goal: unpacking the package and placing the file or folder in the same location as the compressed package.
See Unzip for details.