Explain provabbly fair to a newcomer in one paragraph

[shdama110]

I keep trying to explain provably fair systems to friends and I either overcomplicate it or lose them halfway through. The short version I usually land on: before you play, the site generates a hashed "server seed" you can't see yet, you provide your own "client seed," and after the round the server seed is revealed so you can verify the outcome wasn't changed after the fact.
Curious how other people explain it. What's the simplest, most accurate way you've found to describe it to someone who's never heard of it?

[Arnold070]

Provably fair is a system that allows players to verify that game results haven’t been manipulated. It uses cryptographic hashes based on a server seed, client seed, and nonce to generate outcomes before each bet. After the game, you can verify the result yourself, ensuring that neither the casino nor the player could secretly change the outcome. It adds transparency and builds trust by making every result independently verifiable.

[Kabirjr]

FIFA boy