What's the Definition of Product Market Fet?

The co-founder of wellonfront, eddie rackliffe coined the term product market fet. He was also associated with popularizing the term um and what is it? It's basically the clearer, the the clear demonstration from the market that you'r in to that they clearly want what you're selling. And if you don't know that, and if you say, you know, i'm still a, a putting money into marketing, that's sort of test and learn.