What is the difference between an application server and a web server?

A web server deals with Http protocols and serves the static pages as well as it can ask the helper application like CGI program to generate some dynamic content. A web server handles the client request and hands the response back to the client. An application server exposes business logic to client applications through various protocols, possibly including HTTP. An application server provides access to business logic for use by client application programs. In addition, J2EE application server can run EJBs - which are used to execute business logic. An Application server has a 'built-in' web server, in addition to that it supports other modules or features like e-business integration, independent management and security module, portlets etc.