What is the difference between application server and web server?

Question

What is the difference between application server and web server?

Answer 1

The border between these two are getting ever so thinner.

Application servers expose business logic to clients. That means application servers comprise of a set of methods (not exclusively though, can even be a networked computer allowing many to run software on it) to perform business logic. So it will simply output the desired results, not HTML content. (similar to a method call). So it is not strictly HTTP based.

But web servers pass HTML content to web browsers (Strictly HTTP based). Web servers were capable of handling only the static web resources, but the emergence of server side scripting allowed web servers to handle dynamic contents as well. Where a web server takes in the request and directs it to relevant scripts (PHP, JSP, CGI scripts, etc.) to CREATE HTML content to be sent to the client. Once the content is received, web server will send the HTML page to the client.

However, nowadays both these servers are used together. Where web server takes the request and then calls a script to create the HTML content. Then, the script will again call an application server LOGIC (e.g. Retrieve transaction details) to fill the HTML content.

So both the servers are used effectively.

Therefore .... We can safely say that nowadays, in most of the cases, web servers are used as a subset of application servers. BUT theatrically it is NOT the case.

I have read many articles about this topic and found this article quite handy.