Taxonomy

Every organism gets a binomial name: genus first, species second. Canis lupus and Canis latrans share the genus Canis, meaning biologists have grouped them with other close relatives, but latrans and lupus pin down which exact species inside that genus you mean. This beats a common name like wolf because wolf varies by language and region, while the Latin binomial is fixed and tells you instantly how close two organisms are. Species sharing a genus share more recent ancestry than species that only share a kingdom or phylum.

Taxonomy organizes life into nested ranks, kingdom down to species, each level a subset of the one above it. A cladogram draws this nesting as a branching tree, where each branch point, or node, marks a common ancestor shared by everything branching off above it. Species connected through a shallow, more recent node are more closely related than species that only connect through a deeper, older node further back in time. To find which two species are closest kin, trace each one's branch down to where it first joins another branch; the pair that joins soonest, at the shallowest node, are each other's closest relatives.

A common trap is reading left-to-right position along the tips as a timeline of primitive to advanced. It isn't. Branches can be rotated around any node without changing a single ancestral relationship, so a species drawn on the far left carries no more or less evolutionary history than one drawn on the far right. The only information in a cladogram is which branches share which nodes. This connects directly to classification ranks: the tree is simply a picture of the same nested grouping that genus, family, and order already describe in words.