What is the difference between online and offline shipping methods?

A. Online means that a shipment will have a tracking number, and offline means no tracking numbers are available
B. Online means Magento will use a shipping carrier’s API to obtain rates, offline means Magento will calculate the rates internally
C. Online means that an item’s shipping will be processed by the merchant, offline means that it will be processed by the customer
D. Online means that it will be sent to the customer using a shipping carrier, offline means the customer will pick up the order in person