@globalnomad @Sheril Sounds like you might be using Mastodon's default web interface, the one called the "advanced web interface" (see Fig. 1).
I've included some screenshots, and labeled them in the alt-text, but they should be in the correct order as well.
There's also a one-column layout available that might be more familiar to you. You can access it by unchecking the "advanced web interface" option in the settings (Fig. 2).
The beauty of the fediverse, however, is that nobody is actively preventing anyone from inventing their own way to interpret the user experience. In fact, it's encouraged! For example, there's
https://pinafore.social, an alternative web client developed by
@nolan (Fig.3). I've customized my Pinafore a little bit by adding a black, starry background. That's not something you get by default.
Later, you have the possibility of getting really creative with it. Fig. 4 shows what I'm currently looking at, which is technically Akkoma, not Mastodon, but that's a minor detail. It's a very silly look and feel, but it makes me happy.