Derivatives are actually very easy to understand.
It's a financial mechanism to hedge (aka bet) protecting your position vs someone else position
Kinda like black jack, house wins 49%, betters win 49%, house gets 2%.
HOWEVER, and this is where it gets interesting. Both sides of the "bet" are insured by the same "book". And where it gets really interesting, the book dives into making the bets. Here you have the book (aka too big to fail global bank), making bets, insuring both sides of the bets, and generally creating their own market they are making money on.
Over simplification, yes, but nonetheless accurate.