The SharePoint physical architecture consists of services running on one or more servers.
There are three types of services that together run the SharePoint farm: web, application and database services. Web services through Internet Information Server is what processes the ASP.Net and sends back the html to a user's browser. Application services is where the "brains" of SharePoint are located. All of the SharePoint specific logic and services are processed there. Database services are run by SQL Server and it's where all the data/content for SharePoint is stored.
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