Notes in perfumery are descriptors of scents that can be sensed upon the application of a perfume.
Top notes are perceived immediately upon application of a perfume. They are very volatile, and evaporate quickly. Citrus and ginger scents are common top notes.
Heart notes compound the main body of a perfume and emerge just before the top notes dissipate. They serve to mask the often unpleasant initial impression of base notes, which become more pleasant with time. Lavender and rose scents are typical heart notes.
Base notes are the scent of a perfume that appears close to the departure of the heart notes. Compounds of this class are often the fixatives used to hold and boost the strength of the lighter top and middle notes. Musk and oud are among the base notes.