Microsoft Enterprise Agreement
EA/SA (Enterprise Agreement/Software Assurance) is a volume licensing package offered by Microsoft. It primarily targets large organizations that have 500 or more personal computers. Other programs, including Open Value, Open License and Select License, are geared towards smaller organizations.
The Enterprise Agreement, whose price is tiered to the number of computers being licensed, is a three-year contract which covers all software licensing and updates for one client system. An option is given at contract termination to renew for one or three additional years.
Software products that are licensed under the contract include Windows 10, Microsoft Office and the core Client Access Licenses for Windows Server, Exchange, System Center and Sharepoint, which allow the computer to legally access Microsoft servers over a network.
Microsoft Volume Licensing website, http://www.microsoft.com/licensing/programs/ent/default.mspx