A sensor is a device that detects a physical condition and turns it into an electrical signal or digital information. It helps electronics respond to the real world.
Examples of sensors
Sensors can measure temperature, light, motion, distance, pressure, humidity, sound, touch, acceleration, current, gas, or magnetic fields. Phones, cars, thermostats, robots, and medical devices all use sensors.
How sensors connect to circuits
A sensor may send an analog voltage, a digital signal, or data through a communication interface. A microcontroller often reads that signal and decides what to do next.
In simple terms, sensors give electronic systems awareness.