I don't understand why Panasonic says they invented the inverter technology. Inverter has been around for a very long time. Besides, an inverter is a device that converts DC power to AC power. The Panasonic microwave oven is powered by AC current.
Regular MW works similar to PWM (Paused Width Modulation) power control devices or somewhat similar to FM (frequency modulation) radio signals. .
Inverter MW works similar to AM (amplitude modulation) radio signals.