A set is a collection of items that are unordered and consists of unique elements (meaning they cannot be repeated). This data structure uses the same math concept as finite sets but applied to a computer science data structure.

Let's take a look at the math concept of sets before we dive into the computer science implementation of it. In mathematics, a set is a collection of distinct objects.

For example, we have a set of natural numbers, which consists of integer numbers greater than or equal to 0—that is, N = {0, 1, 2, 3, 4, 5, 6, ...}. The list of the objects within the set is surrounded by {} (curly braces).

There is also the null set concept. A set with no element is called a null set or an empty set. An example would be a set of prime numbers between 24 and 29. As there is no prime number (a natural number greater than 1 that has no positive divisors other than 1 and itself) between 24 and 29, the set will be empty. We will represent an empty set with { }.

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