There are many practical examples of this. One of them is how Twitter and Tumblr show new posts. The number of new tweets or posts is on top of the home page for both, and these home pages get updated automatically without any reloading. Let’s look at Tumblr as an example.
Tumblr has a home icon on the top right that shows the number of new posts. These posts aren’t loaded until the home button is clicked on. This number updates every 10 seconds or so as new posts get posted to your feed that you can choose to see.
Have a look at the image below. We have the network tab open on Safari. The home icon says ‘2,’ which means that there are 2 new unseen posts. We know that the image is a bit small, so please click on it to zoom in if need be.