What's the difference between the money shift and just plain down shifting

Hello All

I'm pretty new to manual cars. Just heard the term money shift. I'm just a bit confused between downshifting (rev match) and the money shift. Why is one damaging and the other is not? Also can you downshift to any lower gear. Example if I'm in 6th can I rev match to 2nd gear? Or is that a money shift

Thanks