Hi colinkgl,
one additional hint: the FDB ist the database file (could be more than one file). If it gets corrupted (and the system might not notice for a while) you will backup a corrupted FDB file. Better to create a .fbk backup (if possible) daily and backing up this. Also, you can copy the FDB file only when the server service has been stopped. Otherwise you will get a corrupted copy. For a copy while the service is running, the program "hotcopy.exe" should be used. But this thing is a PITA in itself.
The .fbk file contains everything the runtime needs to restore a database, when a complete backup has been made. It contains all tabledata and all objects. The one exception I have come across is table 2000000006 "Company". If you have additional fields in this table, they won't be restored (at least not when restoring to a SQL database).
Regarding restore times: I have a customer who has a 40GB native database. Restoring the database from .fbk on a current laptop with SSD runs under 1 hour, on a machine with HDD under a day (or so).
with best regards
Jens