In macOS Mojave, Apple introduced a new notarization feature for apps distributed outside of the Mac App Store that’s designed to further protect users from malicious Mac apps.
Apple is encouraging Mac app developers to submit their apps to Apple to be notarized. An Apple-notarized Mac app comes with a “more streamlined Gatekeeper dialog” to assure users that an app is not known malware.
Apple already provides trusted non Mac App Store developers with Developer IDs that are necessary to let the Gatekeeper function on macOS install non Mac App Store apps without a hassle, but notarization takes it one step further and adds an extra layer of security.
Read more at MacRumors