Small OLED screens for microcontrollers are a cheap and easy way to display more detailed output for your Micro:bit than the scrolling LED matrix allows. Often sold as 0.96″ screens, these are just under 25mm
A rotary encoder, such as the common KY-040 above, is a knob that you can turn continuously either clockwise or anti-clockwise and detect which direction it is being turned. Types such as the KY-040 are
About Buttons Microcontrollers such as the Micro:bit all do one similar thing, accept an input (some sort of ‘message’ from the outside world), process (run some code) and output (show something to the outside world).