what is the use of .includes in js code example

Example 1: javascript string includes

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

Example 2: .includes javascript

let storyWords = ['extremely literally actually hi bye okay']
let unnecessaryWords = ['extremely', 'literally', 'actually' ];

let betterWords = storyWords.filter(function(word) {
  return !unnecessaryWords.includes(word);
});
console.log(betterWords) // ['hi' 'bye' 'okay]