From Office 2007 onwards, there has been a ribbon structure at the top of the opened package with various tabs showing various commands.
On opening Microsoft Outlook on a computer belonging to a client recently, the ribbon showed some icons but not all of them.
Outlook 2016 and Outlook 365 have the options of showing a Simplified ribbon which just shows your most frequently used commands on one line.
To switch between the standard or Classic ribbon and the Simplified ribbon, right-click on the ribbon. Three options will appear – Customize the Ribbon, Collapse the Ribbon and Use Simplified Ribbon.