Pwyll means care or caution in Welsh.
Dyfed, along with Gwynedd, Powys, Ceredigion, Brycheiniog, Gwent and Glywysing (later, Morgannwg), was one of the many petty kingdoms which came into existence in Wales during the post-Roman period. It contained modern-day Pembrokeshire and parts of modern-day Carmarthenshire. However, in 920, during the reign of Hywel Dda, it was amalgamated with Seisyllwg to form Deheubarth.
The name Dyfed was resurrected in 1974 as the collective name for the counties of Cardiganshire, Carmarthenshire and Pembrokeshire, but was withdrawn again in 1996 following further boundary reorganisation.
The cantref was one of the land divisions of Medieval Wales. Traditionally, it contained one hundred (cant) small settlements, each one of which was known as a tref. The cantref was further subdivided into smaller units known as commotes (cymydau) which were themselves divided into smaller units. The cantref has many of the characteristics of the English hundred. Following the Acts of Union of England and Wales, Wales was divided into 90 hundreds, some of which retained the boundaries of the cantrefs.
The seven cantrefs of Dyfed were Cantref Gwarthaf, Cemais, Daugleddau, Emlyn, Pebidiog, Penfro and Rhos. On the map above, several other cantrefs referred to in The Mabinogion can be seen, including Aberffraw, Arllechwydd (sometimes referred to as a commote), Arwystli, Dunoding, Gwent Is coed and Penllyn.