Unison is a file-synchronization tool for Unix and Windows. It allows two copies of a collection of files and directories to be stored on different hosts , modified separately, and then brought up to date by propagating the changes in each replica to the other. Unison can deal with updates to both replicas of a distributed directory structure.
Unison is a file synchronization program. It is used for synchronizing files between two directories, either on one computer, or between a computer and another storage device (e.g. another computer, or a removable disc). It runs on Unix-like operating systems (including Linux, Mac OS X, and Solaris), as well as on Windows.