The terms used to describe the various groups in Northern Irish politics are sometimes misunderstood, and misused.
The two major divisions are Nationlist and Unionist. Nationalist is used to describe those people who wish to see Ireland as a single independent Nation, whereas Unionist refers to those people wishing to see the continuance of the Union between N. Ireland and Great Britain. Current estimates of the population of N. Ireland put the split at roughly 60% unionist, 40% nationalist.
(Note that there is sometimes a subtle difference in whether the word is written with an initial capital or not, e.g. 'unionist' indicating a general connection with the idea, 'Unionist' implying a more direct political involvement especially relating to one of the Unionist political parties.)
The terms 'Republican' and 'Loyalist' will also be heard. Republican imples an extreme form of Nationalism, Loyalist an extreme form of Unionism. The terms are usually used to describe groups who advocate the use of violence to achieve political aims.
Within the two main groups are a number of smaller divisions, usually defined by their representative political parties. This list offers a spectrum of the major parties, from generally 'most pro-Irish' to 'most pro-British" [note, any more accurate voting figures are welcome]
Sinn Fe/in. The political representatives of the Republican Movement. This is the more extreme minority of the nationalist groups, generally regarded as being in sympathy with the IRA's use of violence to achieve political change. Supported by approximately 12% of the population in Northern Ireland, 1.4% in the Irish Republic. Led by Gerry Adams.
The Social Democratic and Labour Party (SDLP). Regarded as the representative of moderate nationalism, it is commited to the establishment of a single Irish nation, but adamantly opposed to the use of violence to force this on people. Its representatives are forthright in their criticism of the IRA and its methods. Supported by approximately 30% of the population in NI. Led by John Hume.
The Alliance party. A centrist party often viewed as unionist in its leanings, but its stated aims are simply to bring people in NI together as one community. Not well supported, it draws support from very moderate unionists, and also from some catholics who feel their future lies with the UK but who cannot support the outright bigotry of some unionist parties or politicians. [voting %?]. Led by John Alderdice.
The Official Unionist Party (OUP). The larger of the two Unionist parties, it is firmly committed to maintaining the links with Great Britian. Not overtly religious in nature, but has close if indirect links with the protestant Orange Order. Drawing support mainly from moderate and middle-class unionists it opposes the use of violence, condemning that from both IRA and Loyalist groups such as the UVF and UFF. Led by James Molyneaux
The Democratic Unionist Party (DUP). Formed in 1971 by Ian Paisley as a breakaway group from the Unionist Party, because of fears that the mainstream party was weak. As to be expected from its fundamentalist leader, the DUP is fiercely protestant and pro-British in character. It draws support from the moderate-to-extreme parts of the unionist population. Although publicly opposed to violence, the same cannot be said for a section of its supporters.