Multiple different kinds of currency, I think – or distinct pots of money in some contexts where it’s relevant that they’re separate. (Are you reading financial/legal documents or something like that?) I’m not sure there is a difference besides spelling preference.

Either that or someone’s affecting an accent. 😛️

It’s the pots/envelopes explanation or income streams is how I hear monies used. Moneys would refer to types of currency since money is an uncountable noun. Like fish and fishes.

https://en.wiktionary.org/wiki/monies

Alternative forms

moneys

Same thing.

Just a funny way to say money. No idea if it can be used in a serious context.