A new version of Office is more complicated for business than it used to be. It includes much more than familiar software like Word and Excel, extending to Office servers (Exchange, Lync, SharePoint and services that run on the latter like Excel Services, Project Services and the Office Web Apps).
There are also hosted versions of these services, provided through third parties and Microsoft itself, as with Office 365. (From March you will also be able to buy Office 365 through Microsoft partners).
Office 365 now includes hosted online services for the Office servers (which also give you the Office Web Apps and Outlook Web App) and subscription licences to the Office desktop software. The consumer Office 365 Home Premium service launched earlier this month and the different business subscription plans become available this week, along with the 2013 versions of Exchange Online, SharePoint Online and Lync Online.
Office 365 Small Business Premium includes Word, Excel, PowerPoint, OneNote, Outlook, Access, Publisher and Lync, with a subscription licence for each user to run them on up to five PCs or Macs at once. You get regular updates and new features for the software and the Office on Demand option lets users download Office to any PC they're using temporarily.
The Office services are similar to existing small business plans for Office 365: Lync Online for audio and HD video conferencing; SharePoint Online for document sharing, collaboration and hosting a public website; plus Exchange Online with a 25GB mailbox for each user and SkyDrive Plus storage (through SharePoint Online).
Office 365 ProPlus (short for Professional Plus), is aimed at small to midsized businesses (10-250 employees) and includes the Office ProPlus versions of Word, Excel, PowerPoint, OneNote, Outlook, Access, Publisher and Lync plus InfoPath (which provides features like PowerPivot and consistency checking in Excel, as well as automated deployment tools).
You get the same Exchange, SharePoint and SkyDrive Plus quotas as Small Business Premium, but it also has integration with on-premise Active Directory for the SharePoint, Lync and Exchange Online services and Exchange Online archiving.
For larger companies, Office 365 Enterprise has the full Office 2013 set of features in both the desktop software and SharePoint, Lync and Exchange Online services, like public folders, legal hold, data loss prevention and rights management to protect confidential information as well as archiving.
If you're already using Office 365 on an enterprise plan (or the simpler kiosk plans for users who don't create content), the differences between the E1 and E2 plans (and the K1 and K2 plans) go away, so users can edit documents in Office Web Apps in all plans.
Enterprise customers will get Yammer integration and be able to purchase the Project Online service when they're available later in the year.