A single coil guitar pickup is usually designed in two ways. The coil can be wound encasing the six small rodmagnets  (Stratocaster design) or with an iron core and the magnet is placed under the coil (P-90 design).

Higher resistance provides more output and in general, the more iron used for the core increase the coil’s inductance. If more windings are used on the guitar pickup it increase the coil’s inductance. More inductance gives a higher output but you loose some treble.
Guitar pickups always use copper wire and a thinner wire with the same amount of windings and everything else being equal gives less bass response. The copper wire used in guitar pickups can be of a wide variety of gauges and the thickness of the insulation used can be varied. The dimension of the copper wire, amount of windings and the general construction of the pickup are all factors that affect the sound of the pickup.

When the string vibrates over the guitar pickup, the magnetic field is disturbed and an electric voltage is generated in the coil. The voltage is then led to the amplifiers input and you hear the result from the speakers.