Regular Charges - This is your fixed monthly rate
Additional Usage - Any usage that has resulted in additional charges, be in long distance, travel / roaming charges or excessive data usage.
Partial Charges - This is typically an additional period of time that is included in your very first bill if you've joined part-way through a billing cycle. Remember you're joining an existing share-group mobility program where billing dates are already pre-established; You do not start your own personal billing cycle when you join. Unless you've joined on the 14th of a month, you will always see a partial charge on your very first bill.