If you've ever read the description of a perfume, you'll know that fragrance related jargon can be pretty tough to crack. Not only have you got to scour through weird and wonderful sounding notes that are impossible to guess the scent of, but in order to get an idea of what the overall perfume smells like you need to understand how the notes work together too. Top notes, heart notes and base notes refer to groups of scents which you can smell after a certain amounts of time, and explains why perfume can smell completely different an hour or two after spraying it on. Here's my very simple guide for how they work- hopefully it gives you a better understanding for when you make your next perfume purchase!
Also known as 'head notes' or 'opening notes' these are the initial notes you smell when you first spray the perfume; the molecules are small and light and evaporate quickly. They tend to be made up of light, fresh and uplifting scents and are generally the less expensive ingredients (which makes sense, you don't want to pay a fortune for an expensive perfume when the smell of the expensive ingredients can only be detected for the first few minutes!) Their scent usually last for between five and thirty minutes; while they don't linger on the skin for a very long period of time it's these notes which you immediately smell when trying a new perfume making them an important selling point. It's always worth waiting for the full time for a perfume to develop before deciding whether or not you want to buy it- but if you can't at least wait for the top notes to evaporate, as the main bulk of the 'wear time' in the perfume is in the heart and base notes.
Heart notes (also known as 'middle notes') make up the core or main body of the perfume and are what you're able to smell after the initial dry down; they take between ten minutes and half and hour to fully develop. Because the heart notes tend to be more mellow they're not always detectable on first spray, which explains how you can initially love/hate a perfume but completely change your mind about it once the fragrance develops. Base notes in perfume can be quite strong, raw and unpleasant but get more pleasant over time, and so the middle notes help to mask this initial scent and provide a transition into the final stages of the fragrance.
Base notes or 'bottom notes' bring depth to a perfume, and can be detected when the light top notes have completely evaporated. It's the middle and base notes that depict the main 'theme' of a fragrance, they work together harmoniously to create the overall scent of the perfume. Base notes consist of large and heavy molecules that evaporate slowly, they're typically rich scents and contain the the most expensive ingredients and perfume oils. These last for the longest amount of time on the skin and help slow down the evaporation rates of the lighter notes, which gives the perfume its staying power.