PREPARING is what WE do ahead of time.
HOARDING is what the idiot down the street says we're doing because he didn't prepare
PREPARING is buying well ahead of time, while there is plenty.
HOARDING is buying much more than you need when an emergency is expeced, and there is not sufficient supply for everybody.
If you buy 100 sheets of plywood for hurricane season in December, that is preparing. If you buy the same plywood two days before the storm is expected, that is hoarding.
Of course, buying with the intent to resell could also easily be considered hoarding. Think "ticket scalpers."