In the Azure portal, we need to create a function app for creating Azure Functions. A function app provides the execution context for individual functions. All configuration done at the function-app level will be applied to all Azure Functions. The following is an example of an Azure Function app named ShipAnyWhere-AzureFunction and a function called UpdateInventory:

These function apps are run and maintained by the Azure App Service platform, which is an Azure service used for hosting web applications, REST APIs, and mobile backends. The following is a layer diagram showing the dependencies of an Azure Functions runtime over other Azure technologies:

From the preceding diagram, it is clear that the root of Azure Functions is the Azure App Service platform, which brings following core capabilities to Azure Functions:

• It provides the ability to configure the application settings used across Functions in a function app
• It provides a console to navigate through all the files in a function app
• Kudu or advanced tools for app services provides access to administrative features of function apps
• It provides built-in authentication capability to use Azure Active Directory and other social providers

The Azure App Service platform was mainly used for web applications, REST APIs, and mobile backends. However, there will always be some background tasks that need to be executed. These background tasks can be achieved by another service called WebJobs, which runs under the context of the same web application. The WebJobs SDK was designed for Azure WebJobs to help them to integrate easily with other Azure services such as Azure Storage, Service Bus, Event Hub, and so on.

Though it was built for Azure WebJobs, the WebJobs SDK can also work independently.

The Azure Function runtime, also called the Azure Function host, can be built from the ground up using the WebJobs SDK. As such, Azure Functions make use of the Azure Function runtime, which is a Webjob.Script (https://github.com/Azure/azure-functions-host) library leveraging the power of the Azure WebJobs SDK and is hosted on the Azure App service platform.