(Answers are in the Teacher's Guide.))
This script is short, but it contains some important instructions that are unique to the micro:bit module hardware.
To begin, the state = 0 statement just creates a variable named state that will be used inside the while True loop.
state = 0
The micro:bit module’s P6 pin is part of the module's 5x5 LED display grid. The display.off() call prevents the LED circuits built into the micro:bit from interfering with the pushbutton circuit you just built on the breadboard.
display.off()
The 10 kΩ resistor connected to the pushbutton is called a pull-down resistor. More about that later! P6 also has an internal pull-down resistor enabled by default, and this statement disables it since a 10 kΩ pulldown resistor has been added to the circuit on your breadboard. Many microcontrollers used in
pin6.set_pull(pin6.NO_PULL)
Inside the main loop, when the pushbutton is pressed, the circuit applies 3.3 V to the P6 pin. The pin6.read_digital() call returns 1 when it detects 3.3 V. If the button is released, the circuit applies 0 V to the pin, and pin6.read_digital() returns 0 instead. In state = pin6.read_digital(), the state variable stores that 1 or 0 result.
while True: state = pin6.read_digital()
Next, the print statement displays "state = " followed by the 1 or 0 that just was stored in the state variable.
print("state = ", state)
Last in the loop, the sleep(250) call just slows down the display to make it easier to observe the transitions from 0 to 1 and 1 to 0.
sleep(250)
The binary (1 or 0) value returned by the pin6.read_digital() method can be used as the argument to turn the LED light on and off in pin13.write_digital(state). When state is 1 because the button is pressed, pin13.write_digital(state) becomes pin13.write_digital(1). This sets the P13 LED light to on. When the state variable is 0 because the button is not pressed, pin13.write_digital(state) becomes pin13.write_digital(0). This sets the LED light to off.
Links
[1] https://learn.parallax.com/sites/default/files/content/Python/button/pb-top-button-digital-read.mp4
[2] https://python.microbit.org/v/2