Data structures are a way to organize data so that it is efficiently accessible for the problem you are trying to solve. Choosing the right data structure will depend on the type of problem you're trying to solve (dictating the manner you access your data), the amount of data you need to organize, and the medium you use to store your data (memory, disk, and so on).
We have already seen and used one example of a data structure. In the preceding sections, we have made extensive use of arrays. Arrays are the most primitive of data structures. They provide access to your data using an index and are fixed in size (also called static). This is opposed to other dynamic data structures that can grow and make more space for data whenever it's needed.