A New Look for Tabs on Salesforce Lightning’s Winter ’17 Release.

The current vertical navigation menu on the left side of Lightning Experience will become a horizontal navigation bar at the top of the page. Users familiar to the Salesforce Classic experience will be right at home, as the updated navigation model will feel very familiar.

The App Launcher is also being redesigned for the Winter ‘17 launch. When users start an App it will present the app’s name, logo, and description on an app tile. The description used to create the app (custom or connected) will be the default text within the app tile. If your organization created custom apps for Salesforce Classic, they will automatically work in this new Winter'17 version.

Can Salesforce Admins opt out of these changes?

For better or worse these changes are permanent and organizations using the Lightning Experience will not be able to opt out.

Is Salesforce1 also getting the interface redesign?

For Winter ‘17 only the Lightning Experience is getting the new navigation user interface.

Why are these changes being made?

Salesforce got a lot of feedback from users and partners saying that the current Lightning experience could be optimized to favor productivity. Therefore, changes are being made to save users time and facilitate access to items they need the most.