Content definitions support groups or repeating structures. This allows a group of fields to be repeated multiple times. For example, a user might have multiple phone numbers or an order might have several products and quantities.
In order to make a group, right click on the "Fields" panel. Select "New group" and call this group "TelephoneNumbers".
Right click on the node called "TelephoneNumbers" and select "New child field ...". This adds a field in to the group. Click the test button, to see a group in action.
Groups consist:

		Label: label to display above the group;
		Hint: Help text for the entire group;
		Minimum occurences: Specifies the minimum number of repeats of this group;
		Maximum occurences: Specifies the maximum number of repeats of this group (-1 indicates no maximum)
		Foreign key: if not empty specifies the foreign key to map the group table to the parent table, see here for more information;