A FO - XSL-FO Form is (as it might suggest) a form that saves data is standard XML format.
If you're wondering what the difference is between XSL-FO and XSL, the answer is nothing. They're both just different names for the markup language that defines how XML data is formatted for whatever media you're working on - whether that's print or screen etc. But, if you're someone who likes to know what all your letters stand for, then XSL-FO is the abbreviation for "Extensible Stylesheet Language - Formatting Objects."
You can integrate FO - XSL-FO Forms (with data you've picked up either online or offline) with any database that supports XML because they use the same standard XML formatting.