Nob or Knob
 

OK, in England, what is a nob? I know it's to do with a stove or hot pot.... but I can only think of a knob to turn the stove top on or off.... anyone know??

I think you're thinking of hob. Nob has several other meanings.

ah, maybe so. So what is a hob as far as cooking is concerned??
https://en.wikipedia.org/wiki/Hob_(hearth)
got it!!
kitchen the hob is a projection, shelf, grate or bench for holding food or utensils at the back or side of a hearth (fireplace) to keep them warm, or an internal chimney-corner. In modern British English usage, the word refers to a cooktop or hotplate, as distinguished from an oven.[1]

I think of a tree root that sticks out of the ground as a nob. The English have many other meanings for nob.

It has been quite eye-opening (or maybe eye-popping!) when I look up some of these things.

I'm thinking my friend meant hot plate. She mentioned cooking problems due to the hob...

Quick google search gave me this definition that fits the cooking reference.

HOB:
....a flat metal shelf at the side or back of a fireplace, having its surface level with the top of the grate and used especially for heating pans. "he laid the empty cup down on the hob by the fire"