ForeFront Identify Manager Client
The User Profile Service is an incredibly powerful part of SharePoint. When used correctly it vastly improves the experience of your users by adding a real sense of personal ownership of your sites and their content.
Unfortunately like any complex system, identifying and fixing issues can be a painful process. There is minimal information provided in the site and almost none regarding the connection between the service and Active Directory.
In SharePoint 2010, the user profile sync is controlled by the ForeFront Identity Manager service, this is a Windows service that handles the connections between Active Directory, any BDC connections defined and the SharePoint site collections and sites.
The workings of the service are somewhat impenetrable, but if you wish to see what it is doing and follow the sync process, it comes with a nice GUI interface.
This can be run directly on the server from the path X:\Program Files\Microsoft Office Servers\14.0\Synchronization Service\UIShell\miisclient.exe
When running during a sync you can see any issues encountered such as permissions problems.
via Chris on SharePoint http://spchris.com/2013/04/forefront-identify-manager-client/
SharePoint and Project Server Consultant