Remember this?

Back in the day when you accidentally stumble upon a cool website that lets's click on Hitler's face as fast as you can until it pops like a balloon and you want to tell your friend so you dial them up and speak out the following "eh t t p colon slash slash dabloo dabloo dabloo dot balooon pop dot com nah use the backward slash".

So what exactly happened to www?

The previous generation of web servers wasn't that smart, to be honest. You had to tell them a lot of stuff beforehand so that they don't mess things up.

Picture a robot that serves you fruit from a basket on command "hand me a fruit" but each time you give the command it hands you random fruit which of course you'll have to put back in 'coz who even likes pomo-grenade? If you want to eat an apple you will have to be a little specific like "hand me an apple".

Previous generation web servers were exactly like this robot. They mostly worked out of single domain example google.com , the domain here is our fruit basket and [mail.google.com, ftp.google.com, google.com] are the fruits. Now mostly when we typed out the URL in our browsers we expected to be served a webpage and www is the keyword for that. Hence, www was just used as an identifier that the client here is looking for a webpage in this vast sea of email, proxy, DNS, database and file servers.

Current-generation web servers are smart. It's like our fruit robot just got an upgrade and has learned all your habits so each day when you say "hand me a fruit" it hands out your favorite fruit apple. Now, whenever you type a URL you don't need to type an additional www because the web server is smart and by default it serves you a web page.

TL;DR: Just like how we don't need to say "dog" every time we see a dog, we don't need to use "www" every time we visit a website.