Britain and Ireland
The British and Irish Isles refer to the islands of Great Britain, Ireland and nearby islands. They are located in Europe.
The Channel Islands are sometimes included in the term "British Isles" because they are a British crown dependency. However, they are located off the coast of Normandy, France, and are not geographically part of the British or Irish Isles.
Until 1922, Ireland was in fact part of United Kingdom. There are several distinct cultures in this island group, however there remain certain cultrual similarities between them, for example the English language is universally understood.
Many of the geographic names have different meanings depending on the context. For example Ireland in legal terms relates to the country Ireland, and not the geographical concept of the Island of Ireland. Similarly, Great Britain sometimes is understood to mean the largest island in the British and Irish Islands, but sometimes is understood to include certain other Islands, which are part of England, Scotland or Wales such as Lundy, Harris or Anglesey.
For further details it is probably best to look at the sections of the individual entities.
Immigration and visa requirements
A number of separate jurisdictions with their own immigration rules make up this region. So a traveller may wish to check the requirments for the territories in which they wish to travel, on the appropriate pages. However there is considerable co-operation and co-ordination between the authorities of the countries in this region meaning that the British and Irish Isles comprise a Common Travel Area, which helps the vast majority of travelers enjoy hassle free travel when crossing borders within the British and Irish Isles.
The Common Travel Area
The United Kingdom, Ireland, the Isle of Man, and the Channel Islands maintain a common travel area, somewhat akin to the Schengen Area on continental Europe. Broadly speaking crossing the borders within the British and Irish Isles is very simple compared with most other international borders.
The arrangment's origins lie in the fact that whole of Island of Ireland was once part of the United Kingdom and so there was never a need for immigration control for what was at that time domestic travel. Whilst Ireland and the United Kingdom have been separate countries for many decades, for the most part both countries have found it more beneficial to maintain relatively open borders. However because of the way its history, the CTA arrangment is not as formalised as other similar arrangments (such as the Schengen Area), and so the exact rules are quite complex for some third country nationals. There are therefore some limited exceptions to the principle of complete freedom of travel.
Throughout this region, traffic drives on the left. In the United Kingdom, and its Crown Dependencies Speed Limits are expressed in Miles per hour. In the Republic of Ireland speed limits are expressed in Kilmometers per hour.