Are you familiar with the term Genealogy ? If not, well genealogy is another word for family tree. Now, are we saying that fragrance has a family tree? You might say so; yes in general fragrance can be group into several categories, depending on the creator or reviewer of the fragrance. We may come across Perfume, EDP, EDT, and EDC. Down the line, each category has lesser degree of fragrance essence or aromatics oil.

Perfume, EDP, EDT, EDC.

These categories are based on the concentration of percent/volume of fragrance essence in the mix.

Parfum (Perfume) 15-40% Dilution
Perfume contains essence of fragrant diluted in the minimum possible amount of high-grade alcohol.
Perfume is the most luxurious and expensive type of fragrance. The high price of perfume is in respect of the higher percentage of fragrance essence within the mix, and the usually luxurious packaging. Don't be surprised that some collectors buy perfume just to collect the bottle and package.
Perfume is generally available in small quantities, often 5 - 15ml. Perfume usually lasts long after first application than other categories like EDP or EDT. Perfume  is intended to last around the clock.

Eau de Parfum (EDP) 10-20% Dilution
A lower dilution of fragrance in alcohol. Eau de Parfum makes a good double-act with EDT, you can start your day with the EDP and then you can replenish it with the EDT.
 
Eau de Toilette (EDT) 5-15% Dilution
The most widely available version of perfume for women or men. EDT is generally available as a spray for ease of use. 
 
Eau de cologne (EDC) 3-8% Dilution
The lightest form of fragrance which can be re-applied several times throughout the day.

Top, Middle and Base Notes

Many ingredients are used to make perfume last long throughout the day. Essentially, as one group of compounds is exhausted, another takes shape. According to this type of genealogy perfume is said to have three notes, which work together to shape a permanent fragrance.

1. The Top Note, the first scent that it permeates,rather strong and remains up to an hour.

2. The Middle Note comes  after the top note lessens and settled in the air and on the skin.

3. The Base Note is the lasting element of the fragrance, after it has been worn for a while. The base note of a fragrance takes time to expand, because it is masked by the the top and middle notes. Overall these three notes of a scent or fragrance work hand in hand to create the expected sensation.