what string.includes return in javscript code example

Example 1: javascript string includes

'Blue Whale'.includes('blue')  // returns false

Example 2: javascript string includes

const s = 'I am going to become a FULL STACK JS Dev with Coderslang';

console.log(s.includes('FULL STACK'));     // true
console.log(s.includes('cheeseburger'));   // false