Previously installing apps on your Mac outside of the AppStore was easy and also very risky and now Apple plans to make this process more secure by using Notarization a new concept introduced in macOS Mojave 10.14.5.
Developers who are new to distributing Mac apps with a Developer ID will need to go through the notarization process for their apps to work on the Mac.
Apple says “Make sure to sign any apps, plug-ins, or installer packages that you distribute to let Gatekeeper know they’re safe to install. And now, you can give users even more confidence in your apps running on macOS Mojave by submitting them to Apple to be notarized.”
You can get more information on Notarization from here.