Olfactive families are groupings of ingredients into broad categories. There are about 1,500 ingredients that a perfumer can choose from, and grouping them into olfactive families helps to identify, memorize, and understand them.
There are a few different models of olfactive classifications, and the one I learned is by Jean Carles, a perfumer and director of the first big perfume school, Roure, in the 1940s. Jean Carles sorts scents into 26 main categories:
CITRIC / ALDEHYDIC / ANISE / WOODY / SPICY / FRESH / AMBERY / FLORAL BALSAMIC / HONEY / SEA / JASMINE / MINTY / ROSE / VIOLET / ORANGE / GREEN leaves / GREEN aquatic / VANILLA / POWDERY / GREEN / MUSK / FRUITY aldehyde / FRUITY / ANIMAL / MISCELLANEOUS
Under each of these would fall all of the ingredients. For example, cedarwood essential oil, vetiver absolute, cedramber and bacdanol would all fall under Woody. Peppermint, menthol and menthone under Minty. And ambergris, civet, and indole (mothballs!) under Animal. Both naturals and synthetics can be categorized in this olfactive family chart.