Living organisms are divided into an hierarchical system of classification. For instance, the Animal Kingdom is divided into several phyla (sing. phylum). Each phylum is further divided into classes, one of which is Insecta.
Each recognised species of organism is known by a scientific name which consists of two parts - its genus name and its species name. So the common house fly is called Musca domestica. This is known as binomial nomenclature. This name is always shown in italics or alternatively is underlined.
Common names do not have scientific validity. Some organisms have no common name - others have several.