No, that's the magnetron. Normal microwave magnetrons have 2 power settings, on and off, and reducing the microwave's power just means switching the magnetron on and off at different intervals.
An inverter just allows to keep the magnetron running at a lower power. Whether that has a better effect than just on/off-switching the magnetron I do not know, but it's probably more energy efficient over long usage periods.
I would imagine having an inverter would allow you to avoid situations where individual parts heat too quickly during your heat cycle, but the advantage probably isn't that big. Afterall, you could just heat it at a slightly lower power to stop whatever overheating effect you're troubled with.