Staged migration is only available to organizations planning to use AD Sync to connect their existing Active Directory to Office 365. It can be used for Exchange 2003 or 2007. You'll need a CSV file of the mailboxes you're moving, as with remote move migration; the wizards in this section will provide you with a template to make one. If you have more than 2,000 mailboxes, this is the migration strategy to use.
If you have Exchange Server 2003 or 2007, but you are not using AD Sync, you'll need to use a cutover migration—unless you have over 2,000 licenses. If that's the case, your situation may be complex enough that you should consult a Microsoft partner for the best way to go forward.
