Variable Racing Ignition MVT Digital Direct Peugeot 103 Electronic

MVT DIGITAL DIRECT Internal Rotor, with light, Peugeot 103 electronic

What is variable advance? And what is achieved by making it variable?
When the engine is at low RPM, it is ideal for the ignition timing advance to be greater, meaning the spark should occur earlier than when the engine is running at maximum speed, where the spark should occur closer to TDC (top dead center) to extract the maximum power from the engine and achieve a more usable power curve.