In JavaScript, a Map is a collection of key-value pairs where the keys can be any datatype and the values can be any value, including objects and primitive values. A Map remembers the original insertion order of the keys, and it has a property that represents the size of the map. The Map object holds key-value pairs and remembers the original insertion order of the keys. The Map() constructor is used to create a Map in JavaScript. The map() method is also available for arrays in JavaScript, which creates a new array from calling a function for every array element. The map() method is useful for iterating over all the elements in an array and making changes to them, resulting in a new array based on what is returned by the function.