<div> problem or something else? (screenshots in comments)

This should be easy fix. I’m currently taking the HTML Beginner to Pro HTML/CSS by Super Simple Dev on YouTube. However, when it comes to using the nested technique, all of my thumbnails/descriptions seem to be going in a vertical order rather than a horizontal order down the screen, could this simply be due to the browser? Or something wrong in my code?

(post deleted by author)

Please post actual code instead of a screenshot.