The ELI5 for Fedora's atomic desktops is that if Windows had an Atomic Desktop version, Program Files and most of the Windows folder would be read only, and each program you installed yourself would go into its own folder in your user directory. That's the basic idea. It's harder to screw up an Atomic system as long as you stick to containerized app formats like flatpak/appimage whenever possible. It makes it easier for everyone to diagnose problems, and easier for users to roll back if an update has problems. Even if you were to install it right now, you could use one simple command to "roll back" to any image from the last three months.

The benefit of Bazzite is you have all of the above, plus a lot of gaming-related stuff preinstalled which, if you were to install them yourself in a normal Fedora environment, you'd likely have to spend a lot of time just learning how they're supposed to be configured, how they interact, which versions have problems, and how to troubleshoot problems when an update to one app breaks a prerequisite for something else; eventually you end up in config hell instead of actually using your computer. With Bazzite, the image maintainers are the ones in config hell - they work out the kinks, app versioning, communicate with upstream to fix issues, all that, so your system should be in the most functional state that a Linux system can be, so you only have to think about using your apps.

tl;dr

• Atomic Desktops are more resilient to randomly breaking from updates or user error, and are easier to revert to a prior state if problems do arise
• Bazzite is a custom Atomic image with lots of gaming stuff preinstalled and preconfigured to work properly out of the box
• If you're a gamer and wanting to try out Linux, Bazzite is going to be the least painful way to get your feet wet.
• Immutable distros are excellent for daily driving. I daily drive one myself!