Arrays are one of the most used Data Structures in JavaScript and pretty much any language. They are a small and simple data structure that is contiguous in memory. Each value is stored right next to each other so you don't have to allocate a lot of space to store data. In JavaScript arrays are resizable and dynamic in nature. In contrast to static arrays in other languages which have a predefined size, you need to move the array over to a different location in memory in order to increase the size.