Taxonomy is the science of classifying all living things. However this is more than just a naming system; on closer inspection it tells the story of all life on earth, a family tree that maps how, and from what, organisms on our planet have evolved in relation to one another.
Although primarily a classification system, taxonomy helps provide a clearer understanding of the often convoluted relationship between different species as they have evolved and diverged from one another.
To understand this complicated system of relationships biologists devised the ‘Phylogenetic Tree’ or ‘Tree of Life’ that divides organisms based on various factors, dividing them into taxonomic levels. It attempts to classify every known organisms, alive or extinct you will have a place on the Tree of Life.
From Crash Course: Biology on YouTube by Hank Green.