The cloud base Microsoft Office 365 combines of Microsoft Office, SharePoint Online, Exchange Online and Lync Online.
According to Mashable.com
There are two editions of Office 365. Office 365 for Small Businesses is designed for organizations of one to 25 people. It’s a pre-built package that includes Office Web Apps, Lync, e-mail sync and more. It doesn’t require IT support on the user’s end and will cost $6 per user per month.
The second version is Office 365 for Enterprises. Unlike the small business version, the enterprise edition can be customized based on an organization’s needs. It can be customized so different teams have different access levels to Office 365’s features. The enterprise edition comes with everything in the small business version, plus single sign-in, Office Pro Plus (via subscription), internal social networking tools, voicemail in the inbox, and more. It costs anywhere between $2 to $27 per user per month, depending on which features the company chooses to utilize.