Windows 8.1 Pro is the operating system intended for small and medium-sized businesses. It provides abilities such as joining corporate domains, participating in Group Policy, allowing involvement in Work Place Join and Work Folders, encryption and more. You can find a good list of business features in the The IT Guide to Windows 8.1. Note that some of the new business features in Windows 8.1 Pro require a server running Windows Server 2012 R2 somewhere in the organization.