Array methods use callbacks to process each element:
let numbers = [1, 2, 3, 4, 5]
// forEach - do something with each
numbers.forEach(n => console.log(n))
// map - transform each
let doubled = numbers.map(n => n * 2)
// [2, 4, 6, 8, 10]
// filter - keep matching items
let evens = numbers.filter(n => n % 2 === 0)
// [2, 4]
You'll learn these methods deeply in the Arrays section. For now, see how callbacks enable powerful patterns.