Great Britain or Foggy Albion, or Britain consists of England, Scotland, and Wales. The United Kingdom of Great Britain and Northern Ireland includes Great Britain and Northern Ireland. The UK is an island state: it is composed of some 5 thousand small islands lie varying distances from the coasts. Geographically, the island of GB is subdivided into two main regions - Lowland Britain (southern and eastern England) and Highland Britain (Scotland, most of Wales, the Pennines, and the Lake District).
The chief rivers of GB are: the Severn, the Themes, the Spey, and the Tweed. The British lakes are generally small and remote. Loch Lomond is the largest lake of Scotland and Loch Ness is the most famous. The largest lake of the UK is at the centre of Northern Ireland - Lough Neagh. The largest lake of Wales - Lake Bala is only 10 sq. km.
The British Flag, known as the Union Jack, is a combination of 3 flags: the Saint Andrew`s cross (the Scottish flag), the Saint Patrick`s cross (the former flag of Ireland), and the Saint George`s cross (the English flag). Political area: monarchy is the desire of English people for preservation of the national unity symbol. The legislature, which consists of both Houses of Parliament and formally the monarch, is the supreme authority, the supreme lawmaking body. The British constitution is an unwritten one. Scotland has its own educational and juridical system.
English is not only one language that is spoken there today. Celtic speech still survives in the British Isles, mainly in the Uplands of Wales and the Highlands of Scotland. In Wales, Welsh is spoken today. In Scotland, Scottish Gaelic. In Ireland, Irish Gaelik or Erse is spoken.
P. S.: More information about the UK of GB and Northern Ireland can be found in the book "British Life" by Anne Collins and in the book "Britain. The country and its people: an introduction for learners of English" by James O`Driscoll.