What is the difference between isotope notation and hyphen notation?

In isotopic notation, the mass number of the isotope is written as a superscript in front of the chemical symbol for that element. In hyphen notation, the mass number is written after the name of the element.
For example, in isotopic notation, the isotope of carbon that has a mass number of twelve would be represented as ${}^{12}\mathbf{C}$. In hyphen notation, it would be written as carbon-12.