What exactly is an Azure Resource Provider?

Question

What exactly is an Azure resource provider?

I'm told I have to register a resource provider for my subscription before I can use a use a particular type of resource, for example to use Event Grid or Key Vault. But, confusingly, there are resource providers and resource types and neither are well explained in Microsoft documentation. For example, Azure resource providers and types starts out by saying:

When deploying resources, you frequently need to retrieve information about the resource providers and types. For example, if you want to store keys and secrets, you work with the Microsoft.KeyVault resource provider. This resource provider offers a resource type called vaults for creating the key vault.

The name of a resource type is in the format: {resource-provider}/{resource-type}. The resource type for a key vault is Microsoft.KeyVault/vaults.

Then it says:

Before using a resource provider, your Azure subscription must be registered for the resource provider. Registration configures your subscription to work with the resource provider.

So, obviously, resource providers are important if I want to work with Azure resources. There is documentation explaining how to register them, list them, which ones are registered with a subscription by default. But I cannot find anywhere that explains what they actually are .

Answer 1

According to Azure Resource Manager - Terminology :

Resource provider - A service that supplies Azure resources. For example, a common resource provider is Microsoft.Compute, which supplies the virtual machine resource. Microsoft.Storage is another common resource provider.

According to azure-resource-provider-sdk :

A Resource Provider (RP, for short) is simply an HTTPS RESTful API contract that Add-on owners will implement so a trusted Azure endpoint can provision, delete, and manage services on a user's behalf. Azure uses the Response from an RP to render and show a set of simple management operations in the Azure Management Portal.