Core Motion primarily handles the accelerometer and gyroscope management for your application through the Core Motion Manager framework. Core Motion also runs in its own thread. The benefits of running in its own thread implies that your application does not have to wait for the Core Motion Manager to send information, and can continue running as and when the Core Motion Manager sends values your application thread can consume, providing a better user experience; as we all know no one likes waiting for information on their devices.
Starting with iOS 5, the Core Motion framework also includes the raw magnetometer data, which was not available to users of iOS version 4.x. It also provides an option to run in the background and access the attitude data. Depending upon which iPhone sensor you are interested in, the Core Motion Manager returns the appropriate Core Motion object.