Goidelic is one of two major divisions of modern-day Celtic languages (the other being Brythonic). It is also known as Gaelic, or Q-Celtic because of the way that words in Brythonic that begin with "B" or "P" begin with "C" or "K" in Goidelic languages.
Although Irish and Manx are often referred to as Irish Gaelic and Manx Gaelic (and it is correct to describe them as Goidelic or Gaelic languages) this is unnecessary because the words Irish and Manx only ever refer to these languages whereas Scots by itself refers to the Germanic language. The word Gaelic by itself is somewhat ambiguous, but most often refers to Scots Gaelic and it is the word that Scots Gaelic speakers themselves use when speaking English. Furthermore, due to the peculiar politics of language and national identity, some Irish speakers are offended by the use of the word Gaelic by itself to refer to Irish. Similarly, some Scots Gaelic speakers also find offensive the use of the obsolete word Erse (i.e. "Irish") to refer to their language.
Goidelic languages were once restricted to Ireland, but in the 6th century Irish colonists and invaders began migrating to Scotland and eventually assimilated the Brythonic language speakers who lived there. Manx, the former common language of the Isle of Man, is descended from the Gaelic spoken in north east Ireland and the now extinct Gaelic of Galloway (Scotland), with heavy influence from Old Norse because of the Viking invasions. Shelta, a cant spoken by the Irish Travellers, is considered its own language even though it is based largely on Irish. Goidelic languages may once have been common on the Atlantic coast of Europe and there is some evidence that they were spoken in the region of Galicia in modern Spain. The Goidelic languages had their own unique script, known as ogham, in use from at least the 5th century until the 15th, especially for carving on wood or stone.
Irish is one of Ireland's two official languages (along with English) and is still fairly widely spoken in the west of Ireland. The legally defined Irish-speaking areas are called the Gaeltacht. At present, Irish is primarily spoken in Counties Cork, Donegal, Mayo, Galway, Kerry and, to a lesser extent, in Waterford and Meath. Irish Gaelic is also spoken by a few people in Northern Ireland and has been accorded some legal status there under the 1998 Belfast Agreement.
Some people in the north and west of Scotland and the Hebrides still speak Scots Gaelic, but because of its minimal official recognition and because of large-scale emigration from those parts of Scotland, the language appears to be in decline. There are now believed to be approximately 1,000 native speakers of Scots Gaelic in Nova Scotia and 60,000 in Scotland.