There is a lot to see and use on AGOL and navigation is key. The User Menu refers to the items along the top of the AGOL Page. Click one of the User Menu Items to learn more.
User Menu Items:
User Menu Icons:
Magnifying Glass: Displays a search bar.
Bell: Displays announcements specific to the user including being added to a Group.
Nine Dots: Displays all AGOL applications available to the user such as Survey123, Story Maps, and Field Maps. 
Account Picture: Displays user settings including My Profile and My Setting.