Messages in new Gmail Inbox are now classified into categories such as Promotions, Social and Updates. You can choose to use categories as inbox tabs, and as labels. These categories make it easy to focus on messages that are important to you and read messages of the same type all at once.
When you receive new mail, you’ll see an indicator in each tab that tells you how many new messages you’ve received since you last checked that tab. You’ll also see a few of the recent senders listed below the category name. You can see what's new at a glance and decide which emails you want to read.