The Orange Order is the largest Protestant organisation in Northern Ireland with at least 75,000 members, some of them in the Republic of Ireland.
The Orange Order is a Protestant fraternity
Its origins date from the 17th century battle for supremacy between Protestantism and Catholicism.
Prince William of Orange, originally of the Netherlands, led the fight against Catholic King James.
He eventually took the throne in England and his final victory over James at the Battle of the Boyne in Ireland in 1690, sealed the religion's supremacy in the British Isles.
In 1795, a clash between Protestants and Catholics at the Battle of the Diamond near Loughgall, County Armagh, led to some of those involved to swear a new oath to uphold the Protestant faith and be loyal to the King and his heirs, giving birth to the Orange Order.
Since then, the order's principles and aims, and those of similar organisations it is related to, have changed little.
It regards itself as defending civil and religious liberties of Protestants and seeks to uphold the rule and ascendancy of a Protestant monarch in the United Kingdom.
The only membership criteria is that an applicant is Protestant.
The order is organised into "lodges". Lodges are created where and when members wish to set them up - Sir James Craig, Northern Ireland's first prime minister, established a lodge at the House of Commons and there have been many linked to British military postings.
Orangeism is also active in former British colonies - principally Canada, New Zealand, Australia and the two west African countries of Togo and Ghana.
The annual 12 July "demonstrations" across Northern Ireland, the most important date in the Orange calendar, commemorate that victory at the Boyne.
Twelfth of July is climax of the marching season
At the heart of Orangeism is the right to parade - and the argument about what those parades stand for.
Orangemen and women say that the parades are intrinsically linked to their culture and community, be it a public statement of faith, a commemoration of those who gave their lives in war or the annual Twelfth of July festivities.
They stress that for decades there was no dispute from the Catholic community over routes and timings of parades.
Opponents of the organisation say the parades stand for bigotry and sectarianism and symbolise a Northern Ireland organised to uphold the rights of only one part of the population.
They argue that opposition to parades has grown as the Catholic community has asserted its right not to be subjected to the whims of one section of the community.
The Orange Order has never been simply a religious organisation.
When the Home Rule movement emerged in the 19th century, the Orange Order steadily moved towards the unionist position.
The organisation opposed Home Rule and partition but concluded that the newly created Northern Ireland would be the defender of its cultural, civil and religious rights.
The first unionist Members of Parliament were drawn from the ranks of the loyal orders.
Dispute over Drumcree parade has made world headlines
Almost every minister in the Northern Ireland government from 1921 until the imposition of Direct Rule in 1972 was an Orangeman.
As the violence of the Troubles deepened, the Orange Order supported the security forces against republican terrorism and its members opposed any political agreement seen as ceding ground to republicans or giving Dublin a say in Northern Ireland affairs.
During the early 1990s, republicans began attacking rural Orange halls, particularly in County Armagh, raising fears among the organisation that its members were threatened with being forced out of areas.
But at the same time, the Orange Order was faced with some members displaying an ambiguous relationship towards loyalist paramilitaries and their activities.
The Orange Order has had historic links with the Ulster Unionist Party. In previous years, it sent about 100 delegates to meetings of the party's ruling council.
However, in March 2005 the Orange Order formally cut its links with the party, ending 100 years of ties.
The order said because of restructuring within the Ulster Unionist Party, it would have to make "impracticable changes" to its constitution.
The decision to reject the Good Friday Agreement had placed the organisation closer to Ian Paisley's DUP than the pro-agreement Ulster Unionists and led to some members questioning whether or not the institution had become too political.
Last year's march in Portadown passed off peacefully
Nowhere was this polarisation seen more than at Drumcree in Portadown.
The route of the march, one of the oldest annual parades by the order, took on a symbolic meaning for both communities out of all proportion with its actual importance.
The Drumcree dispute has not only put the organisation at loggerheads with the Catholic community - but also with the forces of law and order which it, ironically, saw as one of its closest allies.
In 2000, one senior Orange figure said that the order was losing moderate members because it was increasingly dominated by politics, "ignorance and malevolence".
Images of protesters blocking traffic while brandishing Orange regalia with loyalist paramilitary figures in the background were causing a drift away from the order, he said.
Other members traced the change to the summer of 1998 when some of the worst violence associated with Drumcree was witnessed.