Google bought Sparrow (makers of a popular Gmail app for desktop and iOS), and the whole team was put to work on improving Gmail in mid 2012. Today, the results of that acquisition come in the form of a major update to Gmail for desktop and mobile devices. This update is a new smart inbox system that attempts to curb the clutter in your Gmail inbox by allowing you to group your mail according to categories, which appear as tabs.
This new system supports up to five tabs at the same time, and they're also customizable so you can choose the categories you want displayed. The four default categories that Google has defined to help users start organizing emails easily are Primary, Social, Promotions and Updates.
The Primary tab will contain important email, or mail that aren't sorted by any of the categories. The Social tab will contain updates from the social media sites that you visit, while the Promotions tabs will be promotions from online shopping sites you've subscribed to. Finally, less important mail like receipts, bills and updates will be channeled to the Updates Tab. Remember we mentioned five customizable tabs? The last one is a category of your choice.
Some manual sorting is required at the beginning, but once you let Google know which messages belong where, and how important they are, the system should be able to gauge where new incoming mail ought to go. We find that this method of sorting mail is much easier for casual users, while advanced users can add on to this system with multiple filters or colored tabs.
The new inbox is rolling out gradually. The desktop, Android and iOS versions will become available within the next few weeks. If you'd like to try out the new inbox on Desktop sooner, keep an eye on the gear menu and select Configure inbox when it appears in the Settings options.
Users who find that this new inbox management system unsuitable for the way they manage email, can easily switch back to other inbox views that they're comfortable with.
Source: Official Gmail Blog