What are power supply?

Answer 1

A camcorder's power supply is usually a battery that attaches to the back of the camcorder. That battery is most often rechargable from a separate charging pack that comes with the camera.

Answer 2

Power supplies are typically thought of as electronic or electrical equipment which changes the form of a source of power into a form which is acceptable for use by equipment that performs a useful function.

For example, in the typical home, power is available at electrical wall outlets in the form of 120 volts, 60 Hz alternating current (in the United States). This means that electrical current with RMS amplitude of 120V is constantly reversing in direction 60 times per second. This is the way the electrical power is generated by rotating machinery at the utility company.

But this form of power is not directly useful for electronic equipment which typically requires a constant voltage level of some amount, perhaps 12 volts direct current. The role of the power supply, in this case, is to change the form of the power from the alternating voltage to a constant voltage at 12 volts.