Microsoft Windows Server 2008 is the most advanced Windows Server operating system yet, designed to power the next-generation of networks, applications, and Web services. With Windows Server 2008 you can develop, deliver, and manage rich user experiences and applications, provide a secure network infrastructure, and increase technological efficiency and value within your organization. Windows Server 2008 builds on the success and strengths of its Windows Server predecessors while delivering valuable new functionality and powerful improvements to the base operating system. New Web tools, virtualization technologies, security enhancements, and management utilities help save time, reduce costs, and provide a solid foundation for your information technology (IT) infrastructure.

What is a User Cal?
A CAL, or client access license, allows someone access to your Server. CALs come in two forms: device and user. Device CALs allow any number of users to access the server through a single licensed device. A user CAL allows one user to access the server through any device using their individual license.

This authorizes an additional 5 users to access your Windows Server 2008 software. Purchasing User CALs might make more sense if your company has a need for employees to have roaming access using multiple devices. Device CALs may make more sense if your company has multiple-shift workers who share devices.