Is a command line software. Unison will synchronize files from 2 different folders from 2 different locations. Basically, users modify files in source folder and does not need to modify them on the second/backup folder. Just run commands and this application will accomplish the task.
Is working on multiple platforms and allows sync between source and destination folder(s) from different machines with different operating systems installed. In this way you can synchronize between Mac and Windows, Windows and Mac, Mac and Linux and so on.
It display warning and conflicts when occurs. Supports fast transfer speed, similar with rsync (Linux).
This makes Unison a reliable command line alternative application that can be used to maintain backups.