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src/blinky/rp-rs.md

@@ -147,3 +147,26 @@ cd pico2-blinky/rprs-blinky
 
 You refer the ["Running The Program"](../running.md) section
 
+## What is PWM?
+PWM stands for **Pulse Width Modulation**. It is a technique used to control the amount of power delivered to a device by adjusting the width of the pulses in a signal.
+
+In PWM, a digital signal switches between **on** and **off** states at a high frequency. The **duty cycle** of the signal determines how long it stays on compared to how long it stays off. 
+
+- **Duty Cycle**: The percentage of time the signal is on during one cycle. 
+  - For example:
+    - 100% duty cycle means the signal is always on.
+    - 50% duty cycle means the signal is on half the time and off half the time.
+    - 0% duty cycle means the signal is always off.
+
+In the above example code, we use PWM to fade an LED.
+
+### Fading Up
+The first loop gradually increases the LED brightness from `LOW` (0) to `HIGH` (25,000). The `delay.delay_us(8)` creates a short pause between each increase, allowing the LED to visibly brighten.
+
+### Fading Down
+The second loop decreases the LED brightness back down to `LOW` (0), again using the same delay to make the transition smooth.
+
+### Pause
+After fading up and down, the program pauses for 500 milliseconds before repeating the cycle, allowing the LED to rest briefly.
+
+Play around by adjusting the `delay` and observe. You can even comment out one of the for loop and observe the effect.