![micro:bit Servo micro:bit Servo](https://cdn11.bigcommerce.com/s-2fbyfnm8ev/images/stencil/500x659/products/397/1671/microbit-accessories1__44842.1539996268.jpg?c=2)
A small motor that moves it's output arm to a position depending on the signal sent to it with a reasonable degree of accuracy & repeatability.
The brown lead with the black croc clip goes on to GND, the yellow lead goes on to the Pin 0, 1 or 2 that is being used. The red lead goes to the battery + and the battery 0V (aka GND or minus) connecting to the micro:bit GND to provide a common ground. See circuit at bottom of page.