ASP.NET Worker Process

ASP.NET runs within a process known as the ASP.NET worker process. All ASP.NET functionality runs within the scope of this process. Worker Process (w3wp.exe) runs the ASP.Net application in IIS. This process is responsible to manage all the request and response that are coming from client system. All the ASP.Net functionality runs under the scope of worker process. When a request comes to the server from a client worker process is responsible to generate the request and response. In a single word we can say worker process is the heart of ASP.NET Web Application which runs on IIS. A regular Web server contains only a single ASP.NET worker process. This is different from both Web farms and Web gardens:

"Process which is responsible for all asp.net requests and response cycle is known as worker process."