EM is the ability for a user who logs into a phone to retrieve all user profile characteristics as number , speed dialing, line appearance, calling priviliges(Partition/CSS), MWI and so on.
EM is enabled using XML-based services and relies on the Cisco Call Manager / Cisco Database Layer Monitor services and runs as a Tomcat web service in order to function.
Be careful as because the profile is specific to a device (phone) type, it will work only when user logs in to that specific type of device.