Google is to roll out another change to Gmail inbox. I know some people that just hate it when things keep changing, even if there is a benefit.
On the desktop, the new inbox groups your mail into categories which appear as different tabs. You simply choose which categories you want and voilà! Your inbox is organized in a way that lets you see what’s new at a glance and decide which emails you want to read when. Google Gives Gmail a New Desktop and Mobile Inbox For Greater Mail Control [gmailblog.blogspot.com]
In the Gmail for Android 4.0+ and Gmail for iPhone and iPad apps, you'll see your Primary mail when you open the app and you can easily navigate to the other tabs.