The throw-out bearing, or clutch release bearing as it's sometimes called, is located between the clutch fork and the pressure plate fingers. The throw-out bearing only operates when the clutch pedal is depressed; the bearing is not designed for continuous use.
When the driver steps on the clutch pedal, the throw-out bearing applies force to the fingers of the spinning pressure plate to release the clutch. When the clutch pedal is released, the bearing sits idle and does not contact the pressure plate fingers.
The classic symptom of a worn throw-out bearing is a whirring or growling sound when applying the clutch pedal, which goes away when releasing the pedal. Premature wear of the throw-out bearing can occur when there is insufficient clutch play, resulting in a throw-out bearing that spins continuously. If the bearing fails, it may seize and quickly wear the fingers of the pressure plate. The throw-out bearing does not require routine maintenance, but should be replaced when clutch replacement becomes necessary. Consult a professional technician to determine whether the throw-out bearing or other parts of the clutch assembly need replacement.