The document defines and provides examples of different types of sets and numbers, including: 1) Sets can contain distinct objects and are defined using roster notation or set-builder notation. A set is a subset of another if it contains the same elements. 2) The union of two sets contains elements that are in either set, while the intersection contains elements in both sets. 3) Natural numbers are closed under addition but not subtraction. Integers are closed under both. Rational numbers can be expressed as fractions and are closed under all operations. Irrational numbers have non-terminating, non-repeating decimals. 4) The real numbers contain rational and irrational numbers and can be represented on a number