A CPack is a content package that other script authors have uploaded because they want to share it with you, so that you may use it in your mission. A CPack may contain anything that can be expressed in files, e.g. scripts, images, sounds etc.
Maybe you want to add some traffic to your mission. You go to this page and search for "traffic", and find an interesting package created by Engima and named "Engima.Traffic".
In the TypeSqf editor, open the CPack Console and type in the following:
Install Engima.Traffic
Done!
Start your mission and enjoy the traffic!
When you install a CPack in your mission, files are downloaded and installed (unzipped) into different folders in your mission folder. If needed, CPack author has also chosen to add code lines into one or more of the mission's init files.
As a result, if no file conflicts are detected, script is included into your mission.