Data Deduplication is a feature that can be installed on Windows Server 2012 Onwards, it allows files to be only saved to disk a single time but the reference of them will remain intact. When you have a lot of files on a network share this can be very handy to free up some of that expensive SSD Storage space ;)
Just a simple follow through guide. Nothing very technical about it.
Be careful when picking backup software that also supports data dedup tho or you could end up with corrupt files.