Inputs and outputs are an important part of any computer system. As a very small computer, the BBC micro:bit has plenty of inputs and outputs to learn about and use. A processor is sometimes called the brains of a computer and your BBC micro:bit has a micro processor inside it. It's an essential part of your micro:bit as it runs the programs you write.
Your BBC micro:bit has a display of 25 LEDs for you to program, two buttons you can program, and a reset button. The accelerometer in your BBC micro:bit detects when you tilt it left to right, backwards and forwards and up and down. Your BBC micro:bit also has a temperature sensor inside the processor which can give you an approximation of the air temperature and LEDs to sense the levels of light to let you program your micro:bit as a light sensor. Your BBC micro:bit has an inbuilt compass that can detect the direction in which it is facing. Description from Micro:bit.