Switches are electromechanical devices that are very necessary in electronic circuits.
Their primary purpose is to break the circuit, either interrupting the current or diverting it from one conductor to another.
In a switch, the contacts can either be ‘open’ or ‘closed’. Open means that the contacts are not together and non-conducting. Closed means the opposite: the contacts are touching and therefore electricity is flowing between them.
There are many different uses for switches. For example, switches can be operated by variable conditions like pressure or temperature. In this example, they are functioning as a sensor to control an operation. Some switches operate automatically and are used to control motion or machines. Still others are manually manipulated by people for use as a control signal or to control power in a circuit, like a light switch.