The Flexible Single Master of Operations Roles are an important part of the Windows 2000 and Windows 2003 Active Directories. The Active Directory is designed to by a multi-master replication model (with loose consistency and convergence) to ensure that you are not dependent on any one domain controller for day to day functionality. The problem is that not all domain controllers are required to have the exact same data at the exact same time. To help you manage your domain, Microsoft gives you five FSMO roles and this series is a great overview of using these roles.