An installation kit created by a third-party developer. A repack can be designed to reduce the size of the original distribution through more efficient compression methods, or to place multimedia content in other containers.
Computer pirates, too, release own builds of licensed programs. Such repacks usually include a crack to bypass the protection system.
Another repack option is to create installation kits out of different applications from a range of vendors. For example, additional utilities missing in the original distribution can be included in the operating system build.
Regardless of the stated purpose, repacks can pose a threat and contain malware.