An array or list is a way to store multiple variable in one variable, this can be used to store a list of related variables or just a list of numbers. Lists can also be joined together, split apart, or just accessed one index at a time. An index refers to the position in the list where a certain variable sits. Lists are indexed from 0, so the first element is at index 0 then the next is at index 1 and so on.
var myList = [1, 2, 3, 4]; console.log(myList);
var myList = [1, "two", "three", true]; console.log(myList);