Eau de Toilette and Eau de Parfum?
What to consider: "The intensity of essential oils is greater in eau de parfum than in eau de toilette," says Mary Ellen Lapsansky, executive director of the Fragrance Foundation, in New York City. Since eau de parfum is heavy on oils and light on alcohols, it will last longer on your skin―and also cost more. (Eau de cologne is actually the least concentrated of scents but can be used interchangeably with eau de toilette.)
Bottom line: You need only one. Choose based on your desired level of intensity (and price range).