JavaScript works with different types of data. The most common ones are strings, numbers, and booleans.

A string is text:

const name = "John";

A number is a numeric value:

const age = 25;

A boolean represents a true or false value:

const isLoggedIn = true;

There are also two special values: null and undefined.

undefined means a variable has been declared but has no value:

let value;
console.log(value); // undefined

null is an intentional absence of value:

const data = null;

Understanding these types is important because JavaScript behaves differently depending on the type of data you are working with.