Install macOS Mojave for Dark Mode & Dynamic Desktop
One of the biggest macOS Mojave features that you will see when you install the update is Dark Mode and the next is the dynamic desktop.
With the macOS Mojave Dark Mode you get a better focus on the app you are working in, while the rest of the system fades into the background. This is built-in to Apple apps, and they allow third-party support so you can expect to see widespread use. If you prefer the normal brighter view, you can keep that.
No matter which mode you use, the desktop will change during the day, based on the time. You'll see the sun or the moon move across a sand dune. This is an optional feature, and it's kind of like a Live Photo. This will only work with Apple official desktop backgrounds.
With macOS 10.14.4 you now get automatic dark mode activation in Safari for websites that support a dark mode. Once you upgrade this will switch websites, not just safari itself, over to a dark mode automatically. This is a handy feature.