Arrays are a type of variable that allows you to store a group of data in one place. The data is saved in chronological sequence, and the array's size is fixed when constructed. An index number, starting with 0, can be used to access array elements. A list is a means of storing a group of data in a single variable. The data is not saved in any particular sequence, and the list's size can be adjusted as needed. An index number, starting with 0, or a Java iterator can be used to access list elements. Maps are a method of storing a set of data in a single variable. The information is organized into key-value pairs, with the key being a String and the value being any sort of data. A specific key can be searched for in maps, or the data can be sorted in any order. In Java, there are a lot of data structures that are rarely utilized. The skip list, for example, is a data structure that provides for faster searching than a traditional linear list. The binary search tree is another example that enables faster searching than a typical linear list.