Focused Inbox separates your inbox into two tabs—Focused and Other. Your most important email messages are on the Focused tab while the rest remain easily accessible—but out of the way—on the Other tab.

Notes: In Outlook for Windows, Focused Inbox is available only for Office 365, Exchange, and Outlook.com accounts. If you don't see Focused and Other in your mailbox, you might have a Clutter folder instead. For more information, see Use Clutter to sort low-priority messages in Outlook.

Additional information on the Focused Inbox feature is in this Microsoft article.