There are a few main differences between distros and distro families.
Package managers. Debian-based distros like Ubuntu, Mint, and Pop all use apt as a package manager. Red Hat/Fedora-based distros use yum. OpenSuse-based distros use zypper. In decades past, this mattered a lot more. Nowadays, they're all fairly robust and they all handle dependencies effectively.
Package repositories. Every major distro maintains its own package repositories, and some have different priorities. Some distros favor stability over cutting-edge features, only adopting software updates for security reasons rather than cutting-edge features.
Philosophy. Some distros take a hard line on only including free and open-source software in their repositories. Some take a more pragmatic approach, allowing some proprietary software like audio codecs or GPU drivers if you choose. Some favor minimalism for low-end hardware, and some throw in all the bells and whistles.
Update schedules. Some distros are "rolling releases", meaning they receive updates constantly. Most distros have a scheduled upgrade cycle, and some have "long term support" (LTS) releases. Generally speaking, rolling releases are more cutting-edge but potentially less stable, and LTS releases are the reverse.
Default configs. Even though basically all distros can run all the same software, they can preconfigure them differently. Ubuntu's Gnome may look very different from Fedora's Gnome, for example, even though they are the same software and could be configured the same way if you so desired. Also, some distros will default to BTRFS for the filesystem and others will default to ext4, and while you can generally use whatever you want on any distro, you may find that diverging from the default will make your life a little more difficult.
Third-party support. If you are in an enterprise environment, you're probably either a Red Hat shop or an Ubuntu shop, because those are the two distros third-party vendors typically support. "Support" in this case doesn't necessarily mean it won't run on other distros, but if something goes wrong, you're on your own. This can be a problem even in the consumer space. For example, I could not easily get UE5 to run in OpenSuse, and since they only officially support Ubuntu I was on my own.
Community support. This is particularly important if you're new to Linux. If you stick with a popular distro, you are more likely to get relevant results when you google something like "how do I install X on Y". There's a lot of information available for Ubuntu. Not so much if you're running, say, Justin Bieber Linux.
Similarly, there are over 400,000 species of beetle in the world. They're all different, but unless you're a entomologist, you'd be hard-pressed to tell most of them apart.
Thank you! That's very through. I've tried a few distros on VM and as a noob with very easy to fulfill software needs I couldn't see the key differences between the ones I tried out.