What is the difference between isotope notation and hyphen notation?

Hint: Isotopes of elements exist, when any element possesses the same atomic number, but different atomic masses. This happens due to more number of nucleons.

Complete answer:
Isotopes of an element have variable atomic masses. To express these atomic masses along with the element, various notations are used.
Any isotope written in the isotopic notation, involves the atomic mass of that element or isotope of that element, to be written before the symbol of that element in the superscript. For example, isotopes of carbon written in isotopic notation are,${}^{12}C$,${}^{13}C$, and ${}^{14}C$.
On the other hand, hyphen notations are also used to express the mass of a particular isotope. In hyphen notation, the name or symbol of the element is written, and a hyphen is written after which the mass of that isotope form of the element is written. For example, isotopes of carbon written in hyphen notation are carbon-12, carbon-13, carbon-14 or, C-12, C-13, and C-14.
Hence, the isotope notation and hyphen notations differ in writing of mass of the isotope as superscript and after the hyphen respectively.

Additional information: Isotopes contain same atomic number but differ in atomic masses, like isotopes of hydrogen as, ${}^{1}H$ ,${}^{2}H$ , and ${}^{3}H$. While, isobars is the term used to show the element with same atomic mass, and different atomic numbers, like, ${}_{17}^{40}Cl$, ${}_{18}^{40}Ar$, chlorine and argon with same mass of 40 and different atomic numbers.

Note: When the notations around an element are written, then it is to be taken care that it is written before the symbol. The superscript denotes the atomic mass, while the subscript denotes the atomic number. For example, ${}_{6}^{12}C$, carbon has atomic mass of 12 and atomic number 6.