Can someone tell me the difference between the spindle, the hub and the knuckle.

I thought that the bearing on the front driver side of my car went so I bought a bearing online. When I tried to have it pressed on the hub assemble, they told me that the spindle is no good and would have to be replaced.

The spindle they were pointing out or rather showing me is what I would call the hub. I need to know which is which so that I can buy the correct part.


Thanks