"What is the difference between the Republic of Ireland and Northern Ireland?"

Ireland is a single island, situated next to Britain, but there are two countries on the island
The Republic of Ireland makes up most of the island
The Republic of Ireland is an independent sovereign state
Northern Ireland makes up the northeastern part of the island
Northern Ireland is part of the United Kingdom of Great Britain and Northern Ireland
The Republic of Ireland is not part of the United Kingdom
Along with Northern Ireland, the other countries of the UK are England, Scotland and Wales and some smaller islands
The Republic of Ireland is usually referred to as Ireland
When people say Ireland, they usually mean the Republic of Ireland, but sometimes they mean the whole island of Ireland
10)Northern Ireland is usually called the North by people living in the south; while Northerners call the Republic the South
11)Protestants living in Northern Ireland sometimes refer to their country as Ulster, but Ulster is also a larger province, encompassing Northern Ireland and three counties in the Republic
Catholics living in Northern Ireland sometimes refer to their country as the Six Counties, and sometimes call the Republic the Free State