The M274 360 Degree Rotary Encoder Module Brick Sensor is a rotary input device (as in knob) that provides an indication of how much the knob has been rotated AND what direction it is rotating in. It’s a great device for stepper and servo motor control.  You could also use it to control devices like digital potentiometers.

M274 360 rotary Degree encoder, is an incremental electro-mechanical device that converts the angular position or motion of a shaft or axle to digital code. The output of incremental encoders provides information about the motion of the shaft, which is typically further processed in processor/controllers into information such as speed, distance, and position.

Note: This module does not come with a fitting nut or washer , you have to buy it separately (the size required is 6.6mm)