The inductor charging base assembly.

The new Palm Touchstone wireless charger works on the principle of resonant induction. When you move a magnetic field near a coil of wire, it induces a current in the wire.

Taking advantage of this principle, the Touchstone creates an electrical coupling between two coils of wire that are not physically connected. It does this with a primary coil of wire in the base unit which transmits energy to the secondary coil of wire in the phone via a magnetic field.

The magnetic field generated by the base unit flips back and forth rapidly, generating a magnetic pulse that is carefully tuned to the dimensions of the wire coil inside the phone. This oscillating magnetic field induces a current inside the phone, allowing the battery to be charged.

Similar technology is used to transmit power to some battery-operated toothbrushes, razors, etc.