With File Backups you can backup your server files to an external storage. Compared to Provider Snapshots, where the whole server is included in the backup, for File Backups you have the flexibility to choose which files should included (or excluded) from the backup.
No. You can backup files from any server that has SSH enabled.
You can backup any type of files.
Each plan has 5GB, 25GB or 250GB of storage included and you always have to possibility to connect your own cloud storage if you want to replace or extend the storage included in the plan.