docs: added region-related documentation pages (#2845)

* docs: added region doc pages

* docs: small fixes

docs/content/advanced/backend/discounts/index.md

@@ -24,8 +24,6 @@ Discounts can be used in many use cases including:
 2. Creating a sale within a specific period of time (for example, a summer sale).
 3. Give your customers free shipping for a limited time.
 
-![Discounts Architecture](https://res.cloudinary.com/dza7lstvk/image/upload/v1669900544/Medusa%20Docs/Diagrams/discounts_cdxec1.jpg)
-
 ---
 
 ## Discount Entity Overview
@@ -96,6 +94,8 @@ Based on the value of `type`, one of the following relations can be used to retr
 - `product_tags` is an array of product types that this condition applies to if the condition’s `type` is `product_tags`. Each item of the array would be a [`DiscountConditionProductTag`](../../../references/entities/classes/DiscountConditionProductTag.md).
 - `customer_groups` is an array of product types that this condition applies to if the condition’s `type` is `customer_groups`. Each item of the array would be a [`DiscountConditionCustomerGroup`](../../../references/entities/classes/DiscountConditionCustomerGroup.md).
 
+![Discounts Architecture](https://res.cloudinary.com/dza7lstvk/image/upload/v1669900544/Medusa%20Docs/Diagrams/discounts_cdxec1.jpg)
+
 ---
 
 ## What’s Next

docs/content/advanced/backend/regions/overview.md

@@ -0,0 +1,117 @@
+# Regions Overview
+
+In this document, you’ll learn about Regions and their importance in your Medusa server.
+
+## Introduction
+
+Regions represent at least one country on your Medusa server. They're used to define different business logic and configurations for a set of countries.
+
+For example, you can enable one payment provider for region A, and a different payment provider for region B. Customers can then use the payment provider enabled in their region.
+
+This applies to other relations and entities in your store such as different currencies, fulfillment providers, and tax providers.
+
+---
+
+## Region Configurations
+
+The following configurations can be set for each region:
+
+1. The currency used.
+2. The tax provider and rates.
+3. The countries that belong to that region. A country can only belong to one region.
+4. The enabled payment providers.
+5. The enabled fulfillment providers.
+6. The shipping and return shipping options.
+
+---
+
+## One vs Multiple Regions
+
+Your store needs at least one region so that your customers can place orders.
+
+If you serve customers in different countries that use the same configurations, such as the same currency and payment providers, then you can include more countries in the same region.
+
+If you serve customers in different countries that have at least one different configuration, such as different payment providers, you need to create a new region for those countries.
+
+There is no limit on how many regions you can create, and regions can share similar configurations.
+
+---
+
+## Region Entity Overview
+
+A region is stored in the database as a [Region](../../../references/entities/classes/Region.md) entity. Some of its important attributes are:
+
+- `name`: The name of the region. Customers will see this name on the storefront.
+- `tax_rate`: A number that indicates the tax rate. The tax rate is a percentage.
+- `tax_code`: An optional string that is used as the code for the default tax rate.
+- `gift_cards_taxable`: A boolean value that indicates whether gift cards in a region are taxable or not.
+- `automatic_taxes`: A boolean value that indicates whether taxes should be calculated during checkout automatically or manually for that region. You can learn more about manually calculating taxes in [this documentation](../taxes/manual-calculation.md).
+
+---
+
+## Relations to Other Entities
+
+As regions are a core part of your Medusa server, there are many relations to other entities.
+
+This section covers relations to entities that make up the configurations of a region.
+
+![Regions Relations Overview](https://res.cloudinary.com/dza7lstvk/image/upload/v1671465082/Medusa%20Docs/Diagrams/Regions_cg8hsi.jpg)
+
+### Country
+
+A region must have at least one country. A country can belong to only one region.
+
+The relation between the `Region` and `Country` entities is available on both entities:
+
+- You can access the countries that belong to a region by expanding the `countries` relation and accessing `region.countries`.
+- You can access the region of a country by expanding the `region` relation and accessing `country.region`. Also, you can access the ID of the region through `country.region_id`.
+
+### Currency
+
+A region must have one currency. A currency can be used for more than one region.
+
+The relation is available on a region by expanding the `currency` relation and accessing `region.currency`. The 3 character currency code can also be accessed through `region.currency_code`.
+
+### FulfillmentProvider
+
+A region must have at least one fulfillment provider. A fulfillment provider can be used in more than one region.
+
+The relation is available on a region by expanding the `fulfillment_providers` relation and accessing `region.fulfillment_providers`.
+
+### PaymentProvider
+
+A region must have at least one payment provider. A payment provider can be used in more than one region.
+
+The relation is available on a region by expanding the `payment_providers` relation and accessing `region.payment_providers`.
+
+### ShippingOption
+
+:::info
+
+Both shipping options and return shipping options are represented by the `ShippingOption` entity. You can learn more in the [Shipping Architecture documentation](../shipping/overview.md#shipping-option).
+
+:::
+
+More than one shipping option can belong to a region. The relation is available on a shipping option by expanding the `region` relation and accessing `shipping_option.region`.
+
+### TaxProvider
+
+A region can have one tax provider. A tax provider can be used for more than one region.
+
+The relation is available on a region by expanding the `tax_provider` relation and accessing `region.tax_provider`. You can also access the ID of the tax provider through `region.tax_provider_id`.
+
+### TaxRate
+
+A region can have more than one tax rate, and a tax rate belongs to one region.
+
+The relation between the `Region` and `TaxRate` entities is available on both entities:
+
+- You can access the tax rates of a region by expanding the `tax_rates` relation and accessing `region.tax_rates`.
+- You can access the region of a tax rate by expanding the `region` relation and accessing `tax_rate.region`. You can also access the ID of the region through `tax_rate.region_id`.
+
+---
+
+## What’s Next
+
+- Learn [how to use regions in a storefront using the store REST APIs](../../storefront/use-regions.mdx).
+- Learn how to [manage regions using the admin REST APIs](../../admin/manage-regions.mdx).