inetinfo.exe, aspnet_isapi.dll and aspnet_wp.exe in ASP.NET application

What is the role of inetinfo.exe, aspnet_isapi.dll, aspnet_wp.exe in ASP.NET application?

Inetinfo.exe is the executable of Microsoft IIS server. It receives requests and processes/forward them. If the request is received with .aspx extension, ISAPI filter aspnet_isapi.dll takes care of it. This forwards the request to worker process aspnet_wp.exe. This process will actually execute the request and provide response. This worker thread is capable to handle ASP.NET related requests. There can be multiple worker threads running under single instance of IIS.