Using NextPage with an Image?

Can someone explain to me, in simpleton terms, how the following pagination is done?

Example can be seen here – https://www.pinkwhen.com/spring-has-sprung-free-printable/

This gal, I assume, is using the <!–nextpage–> quicktag to create pagination and a ‘click here’ image is used to visit the next page. When you click to visit the next page, you see the entirety of the original post, not just everything you’d assume would be after the <!–nextpage–>. AND you don’t see the ‘click here’ image.

I’d like to accomplish this same thing on my own site, but not sure how to execute it. I feel like I am missing something very obvious in this? I am not sure.

Is she simply adding the intro text, the ‘click here’ image, the <!–nextpage–> quick tag and then adding the intro back in with the rest of the content?

Or is this somehow being executed in php and css? Any help would be most appreciated!