Can Someone Tell Me How This Blog Manages To Do This?

The blog linked below has a gallery that appears to use the built in WordPress upload function. What I wonder is how they get their images to open up full size on a page with a link back to a previous post, because when I use the gallery function it opens the image on a new page but not full size and there is no link back to the post they were viewing which is very annoying.

Here is the site: here and a page showing the an image full size: here.

Thanks 🙂