What are carbon resistors ? What does the colour indicate ?

Explanation

(i) Carbon resistors consists of a ceramic core, on which a thin layer of crystalline carbon is deposited. These resistors are inexpensive, stable and compact in size. Colour rings are used to indicate the value of the resistance.
(ii) Three coloured rings are used to indicate the values of resistors: the first rings are significant figures of resistance, the third ring indicates the decimal multipliear after them.The fourth colour, silver or gold shows the tolerance of the resistor.