schema binding versus XML data binding

I have been able to create a fillable XFA form using XML data and employing the xfa.host.importData(""); script.
This has worked well.

I now find that I must do a similar thing - only using a schema to bind the data to the PDF form fields ...

Can you help me to find out what the differences are between these two approaches and alos can you help me to find some good documentation on how to perform this ?

thanks