There are millions of species on our planet. It would be difficult if we just tried to describe and name each one individually. Although species can be very different from each other, many of them have similar features that allow us to put them into groups.
In the eighteenth century, Carl Linnaeus started the modern system of putting species of organism into certain groups and giving them scientific names. Each species is given a name using Latin words, so that the same name can be used all over the world. For example, the scientific name for human beings is Homo sapiens. Putting different species into different groups according to their features is called classification.