Do you all really wanna treat me as a stupid??? Sorry, but ...
... it is the simple and only "engine and virus definitions update"; it is a small balloon just over the avast tray icon and pops up just after starting up - and then several times a day; you just click "update" to get the latest engine and virus definitions - and that NO INSTALLER, and there is NO REBOOT needed; you just have to close the window after the update was done; that's all. And I would expect not the big window, but just the same small "update done" balloon that appears when setting to automatic update; not less and not more!