One of the new features added to Word, Excel, and PowerPoint is the ability to use Skype for Business (still called Lync on the Mac and iOS) to collaborate and communicate while working on documents. You can IM or video-call someone with Skype from the new Share pane built into the new Office applications.
J. Peter Bruzzese is a six-time-awarded Microsoft MVP, currently for Office Servers and Services and previously for Exchange/Office 365. He is a technical speaker and author with more than a dozen books sold internationally. He's the co-founder of ClipTraining, the creator of ConversationalGeek.com, instructor on Exchange/Office 365 video content for Pluralsight, and a consultant for Mimecast and others.
Microsoft