This has been an interesting topic to have discussions around planning storage and storage requirements organizations need to consider.
FILESTREAM provides a means to consider storage of unstructured data on the File system (specifically NTFS). As we know SharePoint lends itself to allow storage of large binary data, considering FILESTREAM gives us an option of using commodity storage for binary form unstructured data. Again, another way in which SQL Server and SharePoint work together.
The SharePoint Team at Microsoft has done a great job of highlighting the options and explaining the process behind it in a recent post. See it here.