An SPST switch, or Single Pole Single Throw switch, is a basic electrical switch that controls a single circuit. It has two positions: ON and OFF. When the switch is in the ON position, it allows current to flow through the circuit, powering connected devices. In the OFF position, the circuit is open, stopping the flow of electricity. SPST switches are commonly used in household applications, such as light switches and simple electronic devices. They are straightforward to operate and are often found in various forms, including toggle, push-button, and slide switches, making them versatile for different uses.