Azure App Service enables:

• To build and host web apps,
• background jobs,
• mobile backends,
• RESTful APIs in the programming language of your choice without managing infrastructure.
• It offers automatic scaling and high availability.
• This platform as a service (PaaS) allows you to focus on the website and API logic while Azure handles the infrastructure to run and scale your web applications.

Costs

• Pay for resources used by app based on App Service Plan.
• free tier you can use to host small, low-traffic sites.

Types of app services

• Web Apps: Includes full support for hosting web apps using ASP.NET, ASP.NET Core, Java, Ruby, Node.js, PHP, or Python.
• API Apps: you can build REST-based Web APIs using your choice of language and framework. You get full Swagger support, and the ability to package and publish your API in the Azure Marketplace.
• WebJobs: WebJobs allows you to run a program (.exe, Java, PHP, Python, or Node.js) or script (.cmd, .bat, PowerShell, or Bash) in the same context as a web app, API app, or mobile app.
• Mobile Apps: quickly build a back-end for iOS and Android apps. Store mobile app data in a cloud-based SQL database. Authenticate customers against common social providers such as MSA, Google, Twitter, and Facebook. Send push notifications. Execute custom back-end logic in C# or Node.js.