The document discusses the development of the real number system from natural numbers to integers to rational and irrational numbers. It explains that natural numbers were initially used, then zero was added to form whole numbers, and later negative numbers were combined to create integers. Rational numbers include integers as well as fractions and decimals that can be written as ratios of integers. Irrational numbers are real numbers like square roots that are not rational. The real number system consists of both rational and irrational numbers.