Rational numbers are numbers that can be expressed as fractions p/q, where p and q are integers and q is not equal to 0. Examples of rational numbers include 0, -8, -11/3, 5/10, and 9. The document describes how to perform addition, subtraction, multiplication, and division of rational numbers by applying the corresponding properties of fractions. For example, to add rational numbers a/b and p/q, the formula is (aq + bp)/bq.