SENSORS & MODULES
A sensor is a device, module, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. A sensor is always used with other electronics, whether as simple as a light or as complex as a computer.
A sensor is a device used to measure a property, such as pressure, position, temperature, or acceleration, and respond with feedback. For example: A security alarm system may have an infrared sensor which sends a signal when the beam is broken.
Sensor modules have extra electronic circuitry along with sensor that helps interface them with microcontrollers.