Our world is full of sensors, from motion detectors found in security cameras to tiny accelerometers in our smartphones.
Sensors are transducers which undergo transduction, the process of converting sensed energy whether they be movement, sound, light, pressure, heat, etc, into electrical signals. Another transducer is an actuator; However, rather than reacting to the environment, an actuator makes something happen i.e. an LED transforms electrical current into light.
They are also easy to connect up to the Raspberry Pi, thanks to its GPIO pins.
We've got all kinds of sensors and actuators available for your maker projects!