A rational number is any number that can be made by dividing two non-zero integers; in other words it can be written as a fraction p/q where p and q are integers.
This also means that any whole number, terminating decimal, or repeating decimal is a rational number because it can be represented as a fraction (of an integer divided by an integer). If the number cannot be represented as a fraction, then it is called irrational. Such is the case with pi and many radicals (or roots).
An example of a repeating decimal with two repeating numbers is
This number is rational because it can be represented as a fraction of two integers, in this case 37 over 99.