Autodesk® Collaboration for Revit® connects project teams with centralized access to BIM project data in the cloud. Stay connected in real time using the Communicator chat tool within models. With Revit software and Autodesk integration, Collaboration for Revit enables the entire project team to work on shared building information models.
Refer to product overview at http://www.autodesk.com/products/collaboration-for-revit/overview
Autodesk Collaboration v4 for Revit 2017 is an add-on for Autodesk Revit 2017.