Answer:
it works as a summation point of the source
Explanation:
In simple words, The fundamental idea or the central idea refers to the core argument the author makes (also called the primary idea or the primary concept). In other phrases, what all the essay is all about is a core concept. You may conceive of a key concept as a sentence fragment: one phrase that says what the essay is about. There may be more for one core concept for a paragraph.
