The Web server evaluates ASP pages by invoking code in a Dynamic Link Library, called ASP.dll.
The ASP DLL works together with the scripting languages to run your scripts and produce the right HTML code. After the HTML code is generated, it's shipped off to the user's browser.

Server-side scripting is a web server technology in which a user's request is fulfilled by running a script directly on the web server to generate dynamic HTML pages. It is usually used to provide interactive web sites that interface to databases or other data stores.
This is different from client-side scripting where scripts are run by the viewing web browser, usually in JavaScript. The primary advantage to server-side scripting is the ability to highly customize the response based on the user's requirements, access rights, or queries into data stores.