A set is a collection of distinct objects, considered as an object in its own right. Sets are one of the most fundamental concepts in mathematics, and they can be used to model many different situations. For example, a set could be used to represent the members of a club, the countries in Europe, or the planets in our solar system.
There are many ways to define a set. One way is by listing its elements, like this: {1, 2, 3}. This is called an enumeration. Another way is by describing its properties: for example, we could say that the set of all even numbers greater than 10 is {12,…}. Finally, we can also define sets using so-called Set Builder Notation: for instance {x ∈ N | x > 10} denotes the same set as before.