Now that I've summarized the answer in two sentences, let's discuss what they mean. Perfumes are basically very complex mixtures of chemicals, designed to have pleasing scents, as well as to be stable over time and relatively nontoxic. Depending on the scent you want, you'll need to put different mixtures of chemicals into the pot. Perfume design is traditionally not a very scientific process. Basically, people come up with an idea for a smell, and then they mix chemicals together which, from their own experience, might produce that smell.
Perfumes basically are three-part mixtures of chemicals.
The first part, the fragrance, is the one that we usually think about. These are generally esters, aldehydes, or aromatic organic compounds that occur naturally in flowers, fruits, or other things that smell nice. The second part, the solvent, is used to dissolve all the fragrance, and evaporate slowly so that the perfume's scent is given off over a period of time, and not all at once. These are usually common solvents such as acetone or ethanol. The third part consists of stabilizers and fillers, which are used to bulk up the fragrance and make sure that it doesn't degrade over time.