Well, the typical division of the Buddhist schools is into the Southern School (Theravadin) and the Northern School (Mahayana). Why did I use the terms Southern School and Northern School? Because some Theravadin practitioners dislike what they perceive as a kind of criticism of their tradition on the part of Mahayana practitioners. So I have divided the school geographically, which is one of the tradition explications. Within the Mahayana school there are divisions between various traditions but the main one is the common Mahayana, composed of Pure Land, Vinaya, Mind Only and Zen schools (this division has a somewhat Chinese flavor) and the esoteric Vajrayana schools. Here again I could have gone with a geographic hierarchy but this can be less useful than explaining the schools by major focus.
The main focus in the Theravadin schools (the dominant tradition from Sri Lanka->Bangladesh through South East Asia with Vietnam being more Mahayana but a mixture of Theravadin and Mahayana) is personal liberation from samsara typified by the Arhat/Arahant ideal.
The main focus in the Mahayana schools in the cultivation of the Bodhisattva ideal where one seeks the full enlightenment of Buddhahood in order to save all beings from samsara. The Mahayana traditionally stretches from the Black Sea -> Mongolia south to the Southern School countries and over to Japan and Korea but really from Mongolia south (the Kalmyks on the shores of the Aral Sea in Russia are the remnant of the Mongolian Empire that did not later convert to Islam) and including Korea and Japan.
BTW - when I say Mongolia in this context I am including Mongolia people's to the west of Mongolia but not too far south - so the Buddhist people's in Siberia mostly to the West of Mongolia not quite to the Urals.
So this is one way of beginning a conceptual framework of the Buddhist schools.