"Tame" can mean many things in bird adverts. For one seller it means the bird steps onto a hand calmly; for another it only means the bird does not panic when people enter the room. Ask for details and observe the bird yourself.
What real tameness looks like
A tame bird is relaxed around people, accepts gentle interaction and can recover from small surprises. It should not be frozen in fear or grabbed to prove a point. Trust is shown by voluntary behaviour.
How to build trust
Start with routine, distance and rewards. Sit near the cage, offer treats and let the bird choose to approach. Step-up training should be calm and short. Chasing or forcing the bird sets training back.
Buying checks
Ask how the bird was raised, whether it eats independently and how it behaves with different people. A young bird should not leave before it is fully self-feeding. For broader checks, read buying a bird.