SmartLinks simplify the browser experience with Office 365 by allowing for customized URLs.
By default, users accesses the Office 365 Web Apps (ie. Word, Excel, Powerpoint, Sharepoint, Onedrive) by going to a Microsoft Provided landing page. From there, they need to select an App from the tile drop down to access it.
With SmartLinks, you can create your own custom Urls and personalize the experience.