Office Online Apps are lightweight versions of applications such as Word, Excel, PowerPoint, and OneNote that allow for viewing and editing documents. Office Online Apps default to save your documents to your Microsoft OneDrive storage online. These apps also offer better collaboration features than the desktop-based version of Office does. For example, when you collaborate with other people in the desktop version of Word 2013, only one person can edit the same paragraph at a time. Word Online offers real-time editing that allows multiple people to edit the same paragraph at a time.
Because it’s a web application that runs in your browser, Office Online Apps will run on everything, from Linux PCs and Chromebooks to iPads and Android tablets. It doesn’t require any special plug-in and works in any popular browser, including Firefox, Chrome, and Safari — not just Internet Explorer.