What are the suggested "essentials to know" about perfume oil before purchasing a fragrance?

It’s important to understand and appreciate the abbreviations used on fragrances, such as EDP, EDT, the difference between cologne and parfum for example, and the aromatic mixtures that are used in the various perfumes.

• Eau de Cologne is a mixture of perfume oil between 2 to 5%,
• Eud de Fraiche, usually less than 3% perfume oil,
• Eau de Toilette contains 4 to 10% perfume oil,
• Eau de Parfum, between 8 to 15% perfume oil, and
• Soie de Parfum can contain anything between 15 to 18% perfume oil.

Parfum or perfume may also sometimes be referred to as extrait or extract due to its stronger perfume oil content of 15 to 25%. Perfume Oil is 15 to 30% oil based, as opposed to an alcohol base. The alcohol-based perfumes tend to evaporate quicker than an oil based perfume, and as such oil based fragrances are usually longer wearing. Abbreviations such as EDP and EDT make reference to the fragrance strength, for example aftershaves which contain 0.5 to 2% perfume oil as an aftershave is required to cool and calm the skin and a high concentrate of perfume oil may aggravate the skin. Fragrances with the lowest concentration of perfume oil will have less wear, than a fragrance containing higher degrees of perfume oil. The most concentrated perfumes may last up to twelve hours. Where one sees the word "Eau", this refers to a mixture where a lower proportion of oil to alcohol is present and eau refers to water. A concentrated fragrance such as Eau de Parfum or Parfum is similar in term to Parfum de Toilette. In addition to this, some fragrance houses utilise synthetic equivalents for lighter concentrations, and reserve the more costly oils for parfums. One also needs to be aware of the various "notes" used in perfumes, which are the top, middle and base notes