In a typical Azure PaaS cloud solution architecture, the fundamental resource is Azure App Service.
Azure App Service is an HTTP-based service for hosting web applications, REST APIs, and mobile back ends. You can develop in your favorite language, be it .NET, .NET Core, Java, Ruby, Node.js, PHP, or Python. Applications run and scale with ease on both Windows and Linux-based environments. App Service is ideal for 1, 2, and 3-tier applications. In addition to the supported language runtimes you can also bring your own Linux or Windows container.
App Service not only adds the power of Microsoft Azure to your application, such as security, load balancing, autoscaling, and automated management. You can also take advantage of its DevOps capabilities, such as continuous deployment from Azure DevOps, GitHub, and other sources, package management, staging environments, custom domain, and TLS/SSL certificates.*
For 2 and 3-tier applications having a data and storage dependencies, Azure is equipped with managed database services for SQL, MySQL, PostgreSQL, as well as NoSQL and a variety of storage resources.
* https://learn.microsoft.com/en-us/azure/app-service/overview