Short answer is that it means "hummingbirds." A more enlightening response is that in animal classification, Trochilidae is the name of a "family" belonging to the "order" of Apodiformes. (Kingdom, Phylum, Class, Order, Family, Genus, Species). For example,  human beings are "Homo" (Genus) and "Sapiens" (Species). The Blue-throated Hummingbird is in the family Trochilidae, which currently consists of 325 species of hummingbirds, and that number is constantly in flux due to re-classifying existing species and discovering new species.