Dark Mode & Night Themes
Themes shouldn't be new to most Samsung users because they've had a "theme store" on the last several Galaxy phones that lets you change how your phone looks. If you've never tried the Galaxy Theme Store, go do it, we'll wait.
That said, thanks to Android 10 and the Galaxy S10 Samsung finally took things a step further and integrated an entire Dark Mode (Night Mode) to the phone. In fact, they had it on Android 9 Pie, but improved things with Android 10.
Samsung's dark mode works throughout the entire software experience, not just certain apps or interface aspects, but everything is dark and/or black. It's a system-wide dark mode (night theme) that you'll absolutely love. It's something a few other phones have, and now all Galaxy owners can enjoy it.
This is easier on the eyes and will make your battery last longer.