# In this Section:

In this section, we introduce the concept of a set. A set is nothing more than a collection of stuff. We can enclose the elements of a set
(items that belong to a set) inside of curly braces. The order that elements are listed is not important. As an example, the set of even whole numbers less than 10
would be: {0, 2, 4, 6, 8} or we could scramble the order as: {2, 0, 6, 4, 8}. We also discuss many concepts related to the idea of a set. When we have a set, everything
under consideration is known as the universal set. We generally name our sets with capital letters. If one set, let’s say A, contains all of the elements of another set,
let’s say B, and those two sets are not equal, then set B is said to be a proper subset of set A. A set that contains no elements is considered empty; we refer to this
type of set as the null or empty set. Lastly, we will talk about the union of two sets and the intersection of two sets. The union of two sets is a set that contains all
elements of both sets. The intersection of two sets, is a set that contains only the elements of both sets that are common.