Office Online takes all of your favorite Microsoft Office programs and places them on the web. There are online versions of Word, Excel, PowerPoint, and OneNote. These applications run in your web browser, so there's nothing to download or install.
To access Office Online, simply sign in to your Microsoft Office 365 account and click on the application menu in the top-right corner of the site.
Once you’re signed in, you can create new documents or open existing ones in OneDrive for Business. You can share them and work on them with other people in your organization in real-time. In the Office Online programs, you can work together at the same time and see each other’s changes immediately.
You can also open these documents in the Office programs you have installed on your computer, and work on them while they’re stored in OneDrive for Business.