Instead of quotation marks, if a value has brackets around it, that makes it an array value.
var x = [3];
Arrays are a way of storing muliple values of same or different types of values within a single variable. For example, an array could hold a number, a string, and even another array.
let someArray = [1, 2, 3, "A", "B", "C"];
let arrayWithinAnArray =
[1, 2, 3, "A", "B", "C", ["some", "other", "array"]];
array variables hold muliple values in a certain numerical order, objects are slightly more complex and hold named properties and values, but also functions called methods. Arrays can hold variables, strings, and numbers.