What does it mean by 'explain the meaning and underlying idea of a definition or a theorem'?
For example, if we are asked to explain the Fundamental Theorem of Algebra, how should we explain its meaning and idea?
I can only think of saying: The theorem tells us that every single variable polynomial can be expressed into a product of linear factors.
What else should I say? I think I am just stating the theorem, nothing more. I am very confused right now.
To answer your question I want to cite this answer to a question on matheducators.stackexchange.com:
The formal definition or theorem stated in the textbook is the concept definition. You are asked to give also the concept image of the theorem. The following questions might help you:
The answer by Anschewski also links to the book Ideas from Mathematics Education where you might find some help.