What is the difference between application server and web server?

Question

What is the difference between application server and web server?

Answer 1

An application server is a machine (an executable process running on some machine, actually) that "listens" (on any channel, using any protocol), for requests from clients for whatever service it provides, and then does something based on those requests. (may or may not involve a respose to the client)

A Web server is process running on a machine that "listens" specifically on TCP/IP Channel using one of the "internet" protocols, (http, https, ftp, etc..) and does whatever it does based on those incoming requests... Generally, (as origianly defined), it fetched/generated and returned an html web page to the client, either fetched from a static html file on the server, or constructed dynamically based on parameters in the incoming client request.