Product-Market Fit PMF
When a product solves a real need for a specific market so well that growth "pulls itself". The term was coined by Andy Rachleff (Benchmark) and popularised by Marc Andreessen in 2007.
Marc Andreessen's essay: "You can ALWAYS feel when PMF isn't there. And you can ALWAYS feel when PMF is there… The market pulls the product out of the startup." Sean Ellis's "PMF Survey" (asks users: "how would you feel if you couldn't use the product anymore?" — 40 % "very disappointed" = PMF). Rahul Vohra (Superhuman) wrote a famous guide on PMF survey iteration. Pre-PMF: focus on finding it. Post-PMF: scale distribution. Many startups confuse growth hacks with PMF.