Messages in your inbox are sorted into categories, like Primary, Social, Promotions, Updates, and Forums. Categories help you sort your emails so you don’t see all of them at one time. When you open your inbox, you’ll see your Primary tab first
Step 1: Choose your inbox style
In the top right, click Settings Settings and then Settings.
Click the Inbox tab.
In the “Inbox type” section, select Default, Important first, Unread first, Starred first, or Priority Inbox.
Choose other settings, like whether to show importance markers or how to filter mail.
Step 2: Add or remove categories
If you don’t see tabs in your inbox, follow these directions to turn on inbox categories:
In the top right, click Settings Settings and then Configure inbox.
Check the boxes of the categories you want to use. If you hide a tab, those messages will show in your Primary tab.
Optional: Choose whether you want starred messages to show in your Primary tab.