Theravada means the way of the elders, and the name carries an implication about age that needs handling carefully.
Two things are established. The school descends from the Sthavira wing of the early Indian community, and it transmits the Pali canon, the most complete Buddhist scripture surviving in a classical Indian language. What does not follow, and what popular accounts routinely make Theravada say, is that it simply is early Buddhism preserved unchanged. Historians distinguish the ancient Sthaviras from the Theravada identity that formed in Sri Lanka around the Mahavihara monastery, and how continuous the two are is an open question. The tradition's own claim is the more modest one: that it has transmitted the teaching faithfully, not that its history stopped.
The claim in the other direction, that Mahayana is a corruption of something purer, is a sectarian argument wearing the costume of chronology, and this atlas does not make it either.
What is genuinely distinctive is the shape of the path. The goal held up is the arhat, one who has ended the defilements and will not be reborn, not a lesser aim than buddhahood but a different account of what the aim is. The Vinaya, the monastic code, is treated as binding in its detail rather than in its spirit, which is why Theravada ordination lineages can be traced, and argued over, at all. And the commentaries matter enormously: Buddhaghosa's Visuddhimagga, compiled in Sri Lanka in the fifth century, organises the entire path under ethical conduct, concentration and wisdom, and it is through that organisation, rather than directly through the canon, that most Theravada teaching reaches a student.