The 555 timer generates the continuous pulses in astable mode with specific frequency that depends on the value of the two resistors and capacitors. Here the capacitors charges and discharges at specific voltage.
When the voltage is applied the capacitors charges and through a resistors continuously and the timer produce continuous pulses. The pin 6 and 2 are shorted together to re-trigger the circuit continuously. When the output trigger pulse is high, it remains at that position until capacitor is completely discharged. Higher value of the capacitor and resistors are used to attain longer time delay.
These type of circuits could be used in switching the motors ON and OFF at regular intervals or for flashing lamps / LEDs.
