Office 365 comes in different flavours. Office 365 Home Premium is intended for home users and allows Office to be installed on 5 computers. This is the full version of Office, comparable to Office Professional. Office Professional usually costs around £300 to buy whereas Office 365 Home Premium is just £79.99 a year, pretty much making it a no-brainer for a household with multiple computers. Besides the main software, it also provides monthly Skype credit, access to web versions of Office, plus up to 100GB online storage on SkyDrive. When you consider that a 100GB Dropbox account alone is some £70 a year this really helps put things in perspective.
The next version is Office 365 Small Business, aimed at businesses of up to 25 users. This is really an online service as it does not include the Office software itself (although does allow use of the cut-down web-based versions of Word, Excel and PowerPoint). Rather, it provides email, calendaring, conferencing and both private and a public-facing website. Office 365 Small Business is of most interest to small companies wanting a professional email system and who have maybe already purchased the Office software or do not use it. For instance, many small businesses still run an in-house email system established years ago or use services provided by relatively small ISPs; both of these things are less tenable these days and Office 365 provides an excellent alternative with email that works with Outlook, webmail and with tablets and Smartphones. An additional consideration is that Office 365 mailboxes offer use capacity. It costs £39.60 per user per year.
Office 365 Small Business Premium is the same but includes the full Office suite software. Again intended at small businesses with up to 25 users, it is priced at £100.80 per user per year. Both Small Business and Small Business Premium can also be paid for on a monthly basis. Finally there is Office 365 Midsize Business, slightly more expensive, available for up to 300 users. All business versions can be managed from Windows Server Essentials, making it a natural companion, with Office 365 Midsize Business featuring Active Directory integration with Windows Server.