To find them, mouse over the Inbox title on the left of your screen and then click on the drop down arrow to the right of the title. From the drop down arrow, you will see a list of Inbox types.

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The Classic view is what you are most likely looking at right now. It will be in order of date received.

The Important first view will show anything marked as important first and then everything else.

The Unread first view will show all unread messages first and then everything else.

The Starred first view will show anything that is starred and then everything else.

The Priority Inbox view will show Important and Unread first, then Starred and then everything else.