The key point made in a passage is called its idea.

The key point made in a passage is called its main idea.

Explanation:

The main idea -or central idea- of a passage is the most important thought of a paragraph or larger section of a text. Although it may not be clearly stated, main ideas tell the reader what this paragraph or section is about. It is usually a sentence that can be located at the beginning of the paragraph or in any other place within the paragraph.

well there are a bunch of different possibilities so your gonna have to be a bit more specific