Recently I had to transfer the FSMO roles in my Active Directory Domain to a new domain controller. They aren’t a particularly exciting topic or even really all that common in the grand scheme of things. However, if you do Microsoft Active Directory administration, FSMO roles are something you should at least be aware of and preferably know how to work with.
Rather than re-writing what everyone else has already said. Here the links you need to visit to get a good grasp on this topic.
What are FSMO Roles?
How to Transfer FSMO Roles..
How to Seize FSMO Roles
That should take care of most folks!