Software as a Service
A model for the distribution of software where customers access software over the Internet. In SaaS, a service provider hosts the application at its data center and a customer accesses it via a standard Web browser. SaaS is used in a number of common business areas, including customer relationship management (CRM), document management, accounting, human resource (HR) management, service desk management, content management and collaboration. There are literally thousands of SaaS vendors, but Salesforce.com is perhaps the best known example, as it is one of the first vendors to significantly disrupt a traditional software vertical.
An example of SaaS is a web-based version of Microsoft’s Office suite of enterprise-grade applications. Office 365 is delivered to users through the cloud and includes Exchange Online for email, SharePoint Online for collaboration, Lync Online for unified communications, and a suite of Office Web Apps, Web-based versions of the traditional Microsoft Office suite of applications. Office 365 users also have the option of accessing the applications in Microsoft Office 2010 Professional via a monthly subscription
Hosted Exchange (Hosted Email)
A version of Microsoft Exchange Server that is delivered and accessed from a remote server or through a cloud service provider. As in SaaS/cloud-based offerings, Hosted Exchange can be accessed over the Internet. The entire processing of the application is performed on servers in the host datacenter.
Google Apps for Business
Web-based and collaborative Software as a Service (SaaS) solution that customizes the proprietary Google platform and brand for businesses of all sizes, including large enterprises. Google Apps facilitates the provisioning of Google applications and user/enterprise management tools, including Gmail, Google Talk, Google Calendar, Google Docs, Google Videos and Google Cloud Connect.