The Office 365 suite of services includes:
Office Online - web-based versions of Microsoft Word, Excel, PowerPoint, and OneNote that allow you to access documents in a web browser across multiple devices to create and share them online.
OneDrive for Business - individual cloud storage that allows you to easily share files and access them from your mobile devices.
SharePoint - a collaboration, information sharing, and document management service.
Exchange - robust email and calendar, accessible from anywhere.
Skype for Business - connect with others through instant messaging (IM), video calls, and online meetings. (Currently available as a pilot program for eligible users.)