Hi Emma,
Thanks for reaching out to us. I'd like to inform you that the project you've shared above is a 'webpage' project created on the Creative Cloud Express. The creator used multiple features available inside the webpage project, such as photo grids, slideshows etc.
You may refer to this article for getting started with Adobe Creative Cloud Express webpage: https://helpx.adobe.com/express/using/create-web-page.html
Feel free to write to us if any assistance is required; we're here to help.
Regards
Amitej