Office 365 (O365) is the cloud version of Office. Office is a collection of productivity applications – things like Excel, Word and PowerPoint, and so much more – the backbone of Microsoft’s “user” offering (versus the back office offerings like SQL Server, Exchange, and so on).
For some users this is a totally cloud experience – for example a factory worker using browser-based tools on a shared (kiosk) workstation. Others will have the installed Office “desktop” experience on PCs, Macs, and other devices – paid for with a monthly or annual subscription via cloud hosted services, and accessing email handled in the cloud (Exchange Online), accessing files published in SharePoint Online, but also accessing files on their own device (laptop hard disk or whatever). The desktop version allows you to work offline and the next time you connect to the Internet, all your work will automatically sync to the cloud, and you can get automatic upgrades.
All of this – and more – is “Office 365”, and perhaps it is as much about how it is paid for (subscription versus traditional license) as it is about a strict definition of cloud versus on-premises. So O365 can reside completely on Microsoft’s cloud or be integrated with on-premises environments – creating a hybrid environment, in which user accounts, as well as data, can be synchronized for both environments, with password synchronization and single sign-on (SSO) between them.
Office 365 encompasses subscriptions both for home (Office 365 home) and business (Office 365 Business) use, and includes services such as Skype for Business, Exchange Online hosted email, as well as additional online storage with OneDrive for Business. Internet access is a requirement for installing and activating all O365 plans and to manage your subscription, as well as access to O365 cloud services such as email and Skype conferencing.
Microsoft offers FastTrack for O365, providing resources, tools, and experts to make rolling-out O365 a success. Review the O365 Adoption Guide to learn more about creating a successful plan.