The importance of to the rest of Wales was formulated over a few months by a Bangor college lecturer, Owain Owain, in January 1964, when he published in his magazine a map outlining . In an article dated 12 November 1964, he wrote: ('We win , and Wales will be won, and unless is won, it is not Wales that will be won').
<blockquote> The Welsh-speaking, Welsh-identifying group is perhaps most distinctive and largely centred upon the north and west of Wales. This area is designated . The Welsh-identifying, non-Welsh-speaking group is most prevalent in the traditional south Wales area and labelled Welsh Wales. The British identifying non-Welsh speaking group dominates the remainder of Wales, described therefore as British Wales. </blockquote>
A generation or two ago one could say that almost all of western Wales, from Anglesey to parts of Pembrokeshire and Carmarthenshire, lay in the , and that it also included significant parts of western and of the former county of , but today the territory of the language as a majority language has shrunk. A substantial portion of four Welsh counties lies within , which also includes other communities in surrounding counties. The four main counties with a majority of Welsh-speaking inhabitants are , Carmarthenshire ( or in Welsh), and Anglesey (), although even in these counties one cannot say that every town and village is a Welsh stronghold. Surrounding areas often included in the , with a significant percentage of Welsh speakers, include parts of Neath Port Talbot (), parts of western , northern Pembrokeshire (), the uplands of , the uplands and countryside of Denbighshire (), Flintshire () and parts of the district of Swansea ().
Education in is generally through the medium of Welsh, which accounts for about 70% of the school timetable, on average.