Basic principle and Intro

Basic principle noun - Principles from which other truths can be derived.

Intro and basic principle are semantically related. in introduction topic. In some cases you can use "Intro" instead a noun phrase "Basic principle", when it comes to topics like something new.

Intro noun - A short section (as of a book) that leads to or explains the main part.

Basic principle and intro are semantically related. Sometimes you can replace phrase "Basic principle" with "Intro", this terms are similar.