Diagram of normal sinus rhythm as seen on ECG. In atrial fibrillation the P waves, which represent depolarization of the top of the heart, are absent.
The wah-wah pedal is based on a simple concept but its effect is far more dramatic. Using a powerful filter to sweep through a broad frequency spectrum, the wah pedal boosts and exaggerates specific tones. Creating sounds that range from thick, flubbery bass to scratchy, stinging treble.
Overdrive pedals simulate the sound of a tube preamp that has been pushed to its limits and gives a richer soft clipping to the guitar signal. The difference between some soft-clipping distortion a and harder-clipping overdrives is a bit blurred. That is why there are soooo many from which to choose.