Microsoft has announced the general availability of Office Online Server (OOS). Now you can offer the same functionality that you get from the Office 365 experience through your own on premise servers. This means that organizations that would like to offer a browser based experience of their office applications such as excel, word, etc. they can now do so with this new offering without having to have an Office 365 plan.
""OOS scales well for your enterprise whether you have 100 employees or 100,000. The architecture enables one OOS farm to serve multiple SharePoint, Exchange and Skype for Business instances. OOS is designed to work with SharePoint Server 2016, Exchange Server 2016 and Skype for Business Server 2016. It is also backwards compatible