There are many reasons that classifying organisms is important, such as helping understand the genetic relationships between different groups and species, helping with wide studies of organisms and helping to develop new biological sciences such as biogeography. Each of the groups and sets are created by studying the differences and similarities found in species and organisms known.
Overall, about 1.8 million species have been given scientific names with thousands more added to the list each year. Tropical forests and deep seas are thought to contain many of the species that, as humans, we do not know about yet. It is possible that there are anywhere between three and 100 million different species on the planet, though recent reports estimate closer to nine million.