Sharepoint does not work in an isolated fashion. It needs help of two more products IIS (Internet Information Server) and SQL Server.
In order to understand how Sharepoint works with IIS we need first understand the concept of "HttpHandlers and HttpModules". If you are not aware of it you can refresh about the same at,
HttpHandler in ASP.Net: PART 1
HttpHandler in ASP.Net: PART 2
http://www.codeproject.com/KB/aspnet/HTTPHandler.aspx .
Using the HttpHandlers and HttpModules request is first passed through the Share Point runtime and then passed to the ASP.NET runtime (aspnet_isapi.dll).
If you open the web.config file of a Sharepoint enabled IIS web application you can see the application run time handlers and modules.
<httpHandlers>
<add verb="GET,HEAD,POST" path="*" type="Microsoft.SharePoint.ApplicationRuntime.SPHttpHandler, Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" />
....
...
</httpHandlers>
We have highlighted the application runtime module.
<httpModules>
<add name="SPRequest" type="Microsoft.SharePoint.ApplicationRuntime.SPRequestModule, Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" />
...
...
</httpModules>
Use of SQL Server in share point
SQL Server is used to store content and configuration information. We have two types of databases one is the content database and the other is the configuration database. We had said previously that content is according to every site. So every site has his own content database. For instance if we have a payroll site and recruitment site they have their own content database. Configuration database is for the entire site as they are used in web farms, site configuration and lot of other things which are generic and common across all the sites.
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