The question of the role of the British monarchy always comes up when we talk about government types, so it’s nice to have a good, clear explanation. C.G.P. Grey explains the difference between the UK and Great Britain, and untangles the relationship between Britain and its former (and current) colonies.
It’s a fascinating piece of world history. Apparently, Britain is technically a theocracy, because all power is vested in God, and God’s delegate is the monarch. The state religion is Anglicanism.
Update
Grey also has a nice Venn Diagram.