The basics or fundamentals; the essential principles or elements forming the basis of something.
まずは基本をおさえて練習を始めよう。
First, let's master the basics and start practicing.
基本は大事だが、応用力も必要だ。
Basics are important, but applied skills are also necessary.
この本は日本語学習の基本をやさしく説明している。
This book explains the fundamentals of Japanese learning in an easy way.