The fragrance concentration depends on the amount of fragrance oils used in the formula.
The higher the concentration, the stronger the scent will be.
Parfum/Perfume (20%-40%): strongest concentration
Eau de Parfum (10%-20%): high concentration
Eau de Toilette (8%-10%): medium concentration
Eau de Cologne (3%-5%): low concentration
Eau Fraiche (1%-3%): very low concentration