This document discusses different types of real numbers including rational and irrational numbers. It defines rational numbers as numbers that can be expressed as p/q where p and q are integers. Irrational numbers are defined as numbers with a non-terminating and non-repeating decimal representation. Euclid's division lemma and algorithm are explained as ways to find the highest common factor of two numbers. The fundamental theorem of arithmetic states that every composite number can be expressed as a product of primes. Relationships between the highest common factor and lowest common multiple of numbers are also covered. Finally, the document defines terminating, repeating, and non-terminating decimals.