What is this feature? - slide show?

Hi everyone - thanks in advance for your help.
I’m just starting to learn Readymag and am finding features I like and trying to learn them.

I love the feature in this website: The State of Artificial Intelligence | Readymag

What i’m looking to learn how to do is how the pages are seen on the left side and when you click them it reveals the next page.

I’m used to traditional web building and don’t have the vocabulary and know what this is called.

Any help is grat!