What is a method in JavaScript?

A method is a function that belongs to an object.

For example, parseInt is a standalone function – not a method:

const numberAsString = '123';
const parsedNumber = parseInt(123);

console.log(parsedNumber); // 123

While, getFullYear is a function, that belongs to the Date object. It's not standalone, since it is tied to a particular Date object:

const date = new Date(2022, 8, 7);
const year = date.getFullYear();

console.log(year); // 2022