Gmail has introduced a new feature that would automatically categorise your emails in to separate tabs as Primary, Social and Promotions. But if you are not interested and do not want google to decide the category then you can turn off the feature using Gmail settings.
Step 1: Sign in to your Gmail account.
Step 2: Click the Option icon and select Settings from the menu list.
Step 3: In the Settings screen, click Inbox tab and navigate to Categories section. Now unmark the check boxes with caption as “Social” and “Promotions”
Step 4: Click the Save changes button available at the bottom of the Settings screen.
Now you will be back to your old Gmail Inbox with out Primary, Social and Promotion tabs.