When making a payment: Should I create a customer, subscription or charge?
A 'customer object' stores the customer's details (first name, email, payment sources etc.) and the history of all their charges, subscriptions, refunds.
Example: You want to store your customer's details to email them a promo code in the future for your business. You want to store your customer's details to create a charge against them in the future without having to re-enter their payment details.