What exactly is the difference between a frontend and a backend when it comes to websites?

I'm fairly sure that the simplest explanation is that the frontend is what you can see on the website and the backend is everything that happens behind the scenes.

But I'm trying to make my own website and I'm not sure how this distinction applies to it.

The website is not supposed to allow for account creation or anything, its just really supposed to request my instagram posts and more or less display them. (Its an art gallery of sorts)

I'm confused as to whether the requesting is considered backend or frontend. I'm leaning towards frontend because it causes a visual change but then I'm wondering if that's the case, would a website like this even need a backend?