An optocoupler is a small device used in electronics and protection circuitry. It allows two different electrical circuits to communicate with each other without the need of a direct link between the two. It protects delicate components from excess voltage or electrical noise by transmitting signals using light between the two sides.
How Does it Work?
One side has an LED (light)

The other side has a photodetector that receives the light and converts it to electrical energy.
Real-Life Example: Smart Washing Machines
Think about a smart washing machine. The operating board (microcontroller) manages the devices that are used, for example, controlling the water temperature by using low voltage, but the motor and heating parts operate on high voltage.
In case these components were connected together directly, a spike in power could destroy control board. That’s how the optocouplier works by creating a separation between the low-voltage control ands the high-voltage motor and communication is achieved using light. That way, the machine is safe and functional.
Put plainly, to say in simpler words every engineer’s nightmare
