If you use Gmail, you would definitely have noticed the new tabs that separate your emails for you. I gave it a shot for 2 days and had enough of it. An inbox is an inbox — and not two or five. It would have been useful if there was an option to add our own tabs! Here's how to disable this feature, if you haven't done so already.
Go to Settings (the gear icon in the top right) and select "Configure Inbox" from the drop-down menu.
Uncheck any tabs you don't want to appear in your inbox. You can't uncheck "Primary." Click Save.