Just a couple of days after releasing the build to registered developers, Apple on Friday released the first public beta of MacOS Mojave 10.14.2 to testers. This is the same build that was released to developers. Getting it to public beta tests will give broader, more comprehensive feedback on an array of Macs and configurations that will run the new beta code.
Apple generally releases a new beta build for developers first and then waits a day or two prior to releasing it to the public beta group. This is to assure that if there is a show stopping bug that it impacts fewer people and impacts people who are use to dealing with bugs (developers).
As for the contents of this update to MacOS Mojave 10.14.2, it is best to be looked at through the lens of a maintenance build. No new features or functionality have been found so far by testers. This suggests that Apple is tuning performance and other under-the-hood things with Mojave. Of course, we won’t officially know that until the .2 update is released to the public at the end of this year.
If you are registered in the Apple Beta Program, then you should have the update available to you through Settings>Software Update on your Mac. If you want to register, you can do so at the link above but keep in mind that you are using beta software. It is not recommended by Apple or Average Apple Guy that you run it on your production Mac.