What is an application server?

Question

Java

Do I understand correctly what an application server is? In a 3-layer architecture, this is the layer responsible for business logic. On the example of a web application in Java, the application server will be Tomcat + Spring? And at the same time Tomcat will be a web server?

Answer 1

It is best to read about the TCP / IP model, then you will immediately understand what's what. I don’t know where this diagram comes from, but it will confuse you even more, you can safely delete it from all storage media. And so, roughly speaking (on the fingers), let's take a php application as an example.
Request => Web server (nginx) => Application server (php-fpm, for example) => database (if required by the script) => Application server => Web server => Response.