Emergency Updater is the first new feature that is integrated in all three versions of Avast. It has been designed for situations where the Avast updater is not working properly anymore. In the past, this meant that Avast users to to reinstall the whole program to get the updater to work again. With the Emergency Updater integrated into Avast, it is now possible to push updates even if the default Avast Service is not working anymore.
If you wanted to know what this is for look above.