Real numbers include any number that can be found in the real world, such as natural numbers, integers, rational numbers like fractions, and irrational numbers like the square root of numbers. Real numbers are represented by the symbol R and are the union of rational numbers Q and irrational numbers Ǭ. Examples of real numbers include integers, fractions, the square root of 5, and irrational numbers like pi, while complex numbers like √-1 are non-real numbers.