You can think of field groups as product types. Imagine a business with several types of vehicles (cars, boats, and planes). Each vehicle type has a unique set of parameters. For example, for cars, it would be:
In order to create new field group, head over to DJ-Catalog2 Control Panel. Then click "New field group" option.
Now enter name of the field group and its label.
To create new extra field, select New extra field from the control panel.
Now add all necessary informations.