Contains the billing information like subtotal, tax information, customer details, address and email
A line item is an individual entity describing the price, quantity, SKU, title of the product
Customer is the end user who needs the product, it contains the entire details of customer like name, address, email etc
Discount which is applicable on the charge, it contains information of discount like it's applicability and expiration details
Contains address information, customer information, product details, quantity and price
Subscription contains address, customer information along with the expiration details,cancellation details and next billing cycle details
Contains the subscription id and updated date information along with all the subscription table fields