The difference between types of fragrance is the amount or concentration of the oils in it. These oils are commonly referred to as "juice". The higher the concentration of "juice" the longer your fragrance will last and the less you need to apply.
Perfume (or parfum) has the highest concentration of juice, causing the scent to be released over a longer period of time in a series of notes
The second highest concentration is found in Eau de Parfum which has a touch lighter smell to it than perfume.
Next is Eau de Toilette, whose scent is lighter still, so it is fit to apply liberally.
Lastly, Eau de Cologne is the most subtle version of fragrance; however Eau de Toilette and Eau de Cologne are generally interchangeable, particularly in Men's fragrances. After Shave has the least amount of oils.