A <u>central idea</u> of a text is the most important idea.
Explanation:
The <u>central idea</u> or <u>main idea</u> is the most important idea or central thought of a text that helps the reader understand what the text is about. This could refer to what the text is about in its entirety, or at least in various paragraphs or sections. Sometimes, the <u>main idea</u> is directly stated in the text, while some other times, it is implied.