[Pretty Girl]

Subpixel antialiasing, also known as font smoothing, by default. On a MacBook Air or a desktop Mac hooked up to a non-Retina display, upgrading will make your fonts look worse. Update: We’ve found a better method that will actually re-enable subpixel antialiasing rather than just relying on font smoothing. Open a Terminal and run the following command:

defaults write -g CGFontRenderingFontSmoothingDisabled -bool NO

Log out and log back in for your changes to take effect. Thanks to Dean Herbert for reporting this to us.
Here’s the Difference

Subpixel antialiasing is a trick designed to make fonts look better on lower-resolution displays. Without this feature enabled by default, macOS Mojave makes text look thinner and more blurry on non-Retina displays.
(As some eagle-eyed readers have noticed, the below trick doesn’t technically enable subpixel antialiasing. However, this does increase font weight, which makes fonts look less jagged and all-around better on the MacBook Air and other low-resolution displays.)
While subpixel font smoothing is disabled by default, you can re-enable it with a terminal command. There are four possible settings: 0 (disabled), 1 (light smoothing), 2 (medium smoothing), and 3 (heavy smoothing).

defaults -currentHost write -globalDomain AppleFontSmoothing -int 3

[Ronie]

Remove all adjustments to font smoothing in Mac OS and return to default settings

This command will remove any custom font smoothing setting:

defaults -currentHost delete -globalDomain AppleFontSmoothing

This command will revert the change to rendering font smoothing settings back to the default in macOS Mojave:

defaults write -g CGFontRenderingFontSmoothingDisabled -bool YES

Again, restart the Mac or log out and back in again for the change to take effect.

[lorde]

Thanks for the information