# About the Billing APIs

Understand how the Billing API objects work together.

*Subscriptions* automatically create *Invoices* and *Payment Intents* for you. They have the following parts:

* A *Product* to model what is being sold.
* A *Price* to determine the interval and amount to charge.
* A *Customer* to store the *Payment Methods* used to make each recurring payment.

## API object definitions

| Resource                                                                      | Definition                                                                                                                                                                                                                                                                                                                                                                                                    |
| ----------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [Entitlement](https://docs.stripe.com/api/entitlements/active-entitlement.md) | Represents a customer’s access to a feature included in a service product that they subscribe to. When you create a subscription for a customer’s recurring purchase of a product, an active entitlement is automatically created for each feature associated with that product. When a customer accesses your services, use their active entitlements to enable the features included in their subscription. |
| [Feature](https://docs.stripe.com/api/entitlements/feature.md)                | Represents a function or ability that your customers can access when they subscribe to a service product. You can include features in a product by creating ProductFeatures.                                                                                                                                                                                                                                  |
| [Invoice](https://docs.stripe.com/api/invoices.md)                            | A statement of amounts a customer owes that tracks payment statuses from draft through paid or otherwise finalized. Subscriptions automatically generate invoices.                                                                                                                                                                                                                                            |
| [PaymentIntent](https://docs.stripe.com/api/payment_intents.md)               | A way to build dynamic payment flows. A PaymentIntent tracks the lifecycle of a customer checkout flow and triggers additional authentication steps when required by regulatory mandates, custom Radar fraud rules, or redirect-based payment methods. Invoices automatically create PaymentIntents.                                                                                                          |
| [PaymentMethod](https://docs.stripe.com/api/payment_methods.md)               | A customer’s payment instruments that they use to pay for your products. For example, you can store a credit card on a Customer object and use it to make recurring payments for that customer. Typically used with the Payment Intents or Setup Intents APIs.                                                                                                                                                |
| [Price](https://docs.stripe.com/api/prices.md)                                | Defines the unit price, currency, and billing cycle for a product.                                                                                                                                                                                                                                                                                                                                            |
| [Product](https://docs.stripe.com/api/products.md)                            | A good or service that your business sells. A service product can include one or more features.                                                                                                                                                                                                                                                                                                               |
| [ProductFeature](https://docs.stripe.com/api/product-feature.md)              | Represents a single feature’s inclusion in a single product. Each product is associated with a ProductFeature for each feature that it includes, and each feature is associated with a ProductFeature for each product that includes it.                                                                                                                                                                      |
| [Subscription](https://docs.stripe.com/api/subscriptions.md)                  | Represents a customer’s scheduled recurring purchase of a product. Use a subscription to collect payments and provide repeated delivery of or continuous access to a product.                                                                                                                                                                                                                                 |

Here’s an example of how products, features, and entitlements work together. Imagine that you want to set up a subscription service that offers two tiers: a standard product with basic functionality, and an advanced product that adds extended functionality.

1. You create two features: `basic_features` and `extended_features`.
1. You create two products: `standard_product` and `advanced_product`.
1. For the standard product, you create one ProductFeature that associates `basic_features` with `standard_product`.
1. For the advanced product, you create two ProductFeatures: one that associates `basic_features` with `advanced_product` and one that associates `extended_features` with `advanced_product`.

A customer, `first_customer`, subscribes to the standard product. When you create the subscription, Stripe automatically creates an Entitlement that associates `first_customer` with `basic_features`.

Another customer, `second_customer`, subscribes to the advanced product. When you create the Subscription, Stripe automatically creates two Entitlements: one that associates `second_customer` with `basic_features`, and one that associates `second_customer` with `extended_features`.

You can determine which features to provision for a customer by [retrieving their active entitlements or listening to the Active Entitlement Summary event](https://docs.stripe.com/billing/entitlements.md#entitlements). You don’t have to retrieve their subscriptions, products, and features.