A wrong house price

Last lesson: a model is a learned function with knobs (parameters). Now: how do those knobs get set?

You show a tiny price model some houses:

900 sq ft, 2 beds  →  $200K
1200 sq ft, 3 beds →  $280K
1800 sq ft, 4 beds →  $410K

On a new house it guesses $350K. The real sale was $410K. It missed. Training is how it gets less wrong next time.