Industrial Hypertext migrated a large web application that was an ASP.NET CRM (Customer Relationship Management System) that connected to an SQL Server database which was an on-prem installation. We migrated the application to an Azure ASP.NET App Service PAAS (Platform as a Service) and Azure SQL,which is Azure's managed SQL Server solution.
Managed App Services and Databases remove the need for a system administrator to have to build and maintain an operating system and patch the server applications, as Microsoft Azure manages the underlying server and applies updates and security patches automatically.
The original web application we migrated to Azure was a PHP and .NET PostgreSQL/Postgis GIS (Geographic Information System) web app hosted in a cloud Virtual Machine, which was migrated to a Linux App Service PAAS (Platform as a Service) and Azure managed PostgreSQL database (similar to MySQL).
Virtual machines are an easy way to rehost (or lift and shift) a server to the cloud, as like a physical server, they have a regular operating system, and can run any of the apps that a server can.
Managed App Services and Databases remove the need for the client to have to maintain the operating system and server applications, and Azure manages them and applies updates and security patches. It's also very easy to scale up a cloud service by adding more instances as required by the web app's traffic.