Foundation edition: This edition (formally known as Windows SharePoint Services) offers only the core capabilities of SharePoint and is available as a free download from Microsoft (http://www.microsoft.com/en-us/download/details.aspx?id=35488). SharePoint Foundation's only licensing requirement is that each user has a valid Windows Client Access License (CAL).

Standard edition: This includes all of the capabilities of Foundation and adds many capabilities targeted at small- to medium-sized organizations and departments, including additional site templates, and collaboration, enterprise content management, and Search capabilities.

Enterprise edition: This includes all of the capabilities and services that the SharePoint platform has to offer and is targeted at larger organizations. These additional capabilities include the Office services, that is, Access, Excel, InfoPath...