This document defines key concepts in the real number system including rational numbers, irrational numbers, integers, and subsets. It explains that real numbers contain both rational numbers (which can be expressed as fractions) and irrational numbers (which cannot). Various properties are discussed such as comparing and ordering real numbers. Examples are provided to demonstrate plotting numbers on a number line, determining if a number is rational or irrational, and arranging sets of numbers in ascending and descending order.