You can count the number of pulses to tell how much time has gone by. We will see how the 555 timer can be used to generate this clock. A graph of a clock signal is shown below. . If you already understand capacitors you can skip this part. The picture above on the left shows two typical capacitors.
Capacitors usually have two legs.
One leg is the positive leg and the other is the negative leg. The positive leg is the one that is longer. When you put one in a circuit, you must make sure the positive leg and the negative leg go in the right place. Capacitors do not always have a positive leg and a negative leg. The smallest capacitors in this kit do not.