This document provides an overview of different number systems including natural numbers, whole numbers, integers, rational numbers, irrational numbers, and real numbers. It defines natural numbers as starting from 1, whole numbers as starting from 0, integers as containing positive, negative and zero, rational numbers as in the form of p/q where q is not zero and p and q are integers, irrational numbers as including pi and square roots of non-perfect squares, and real numbers as encompassing all other number types.