Windows Phone has in-built support for the document sharing features of SharePoint. SharePoint sites can be added as one the places (documnt store) in the Office Hub, but this represents only partial integration with SharePoint's full range of functionality.
SharePoint is business collaboration platform developed by Microsoft. Traditionally it is associated with corporate website creation, content management and document sharing, but it also includes community building, business intelligence and social elements associated with making it easier for groups to work together.
Social networking and profiles were first introduced in SharePoint 2010, but the newsfeed feature has been comprehensively reworked in SharePoint2013. The new functionality allows users to be post status messages to newsfeeds. Messages can be shared with the whole organisation, a group or an individual. The functionality can be described as an internal corporate equivalent of Twitter or Facebook.
It is this re-imagined newsfeed functionality with which the SharePoint app for Windows Phone 8 integrates. The app allows users to post new status messages, read and like colleagues messages, post replies to messages, upload media, view profiles, and work with followed (shared) documents.
The addition of a SharePoint app to Windows Phone can only further burnish the platform's enterprise credentials. Unsurprisingly no other platform has the range or depth in integration with Microsoft's various enterprise focused services and applications.
SharePoint app description from Windows Phone Store:
The SharePoint Newsfeed for Windows Phone makes it easy to stay connected with your colleagues using SharePoint's social features. You can post to newsfeeds on all your SharePoint sites, follow people, documents, and tags, and more.
SharePoint can be downloaded for free from the Windows Phone Store. It is only available for Windows Phone 8 devices, and is described as a "preview version".