I believe you'd only want to bind a section to a field if you've got a group of radio buttons or checkboxes that pertain to that field. So, if I have a Customers table with a field called Transportation Method, I could have a section linked to the Transportation Method field, and that section could contain three option buttons -- Rail, Truck, Ship.
If I wanted a section that had the contact info from the Customers table (address, city, state, ZIP, phone, etc.), I would bind the section to the Customers table.
Hope that helps!