When a user navigates to google.com, their request specifies the URL but not the filename for today’s Google Doodle. The web application’s back-end will need to hold the logic for deciding which assets to send. Moreover, modern web applications often cater to the specific user rather than sending the same files to every visitor of a webpage. This is known as dynamic content.

When we eat at a restaurant, we’ll order to our tastes, make substitutions, etc; the result is a dining experience unique to us. Aside from that, there’s a lot happening behind the scenes to make a restaurant work: ingredients are ordered from suppliers, new menus are designed, and employees’ schedules are created. Similarly, to make a web application that runs smoothly, the back-end is doing a lot more than simply sending assets to browsers.

The collection of programming logic required to deliver dynamic content to a client, manage security, process payments, and myriad other tasks is sometimes known as the “application” or application server. The application server can be responsible for anything from sending an email confirmation after a purchase to running the complicated algorithms a search engine uses to give us meaningful results.