The on period, known as pulse width, is modulated (a.k.a. changed) via the code, allowing you to control the value sent to your components. PWM pins work the same way across all Arduino boards ...

A 16-year-old, for example, has created a self-driving toy car that’s powered by an Arduino Nano ... “To control the speed of the car he should look up Pulse Width Modulation (PWM).