On a branching tree diagram, animals are broken down Kingdom, Phylum, Class, Order, Genus, Species, Sub-species. (Remember the mnemonic King Phillip Came Over for Grape Soda).
Branching tree diagrams (or cladograms) attempt to show the ancestral relationships between species. The groupings indicate relatedness - closely grouped organisms will be more closely related...
It begins at the base of the tree the common ancestor. And it ends when you the organism or group with the greatest number of shared derived characteristics.