The rotary encoder is a rotary input device that provides an indication of how much and in which direction the encoder has been turned. This 20-pulse Rotary Encoder Breakout has a nice 'clicking' feel and also has a push-button built into it so you can press onto the knob to close a separate switch. It is panel mountable and comes with two mounting holes for securing to your hardware.
The encoder is different from a potentiometer in that an encoder has full rotation without limits. It's a great device for stepper and servo motor control.
This unit does not come with a knob.