how does pop work in javascript code example

Example 1: js array.pop

let cats = ['Bob', 'Willy', 'Mini'];

cats.pop(); // ['Bob', 'Willy']

Example 2: js array.pop

let cats = ['Bob'];

cats.push('Willy'); // ['Bob', 'Willy']

cats.push('Puff', 'George'); // ['Bob', 'Willy', 'Puff', 'George']