Remembrance Sunday falls on the closest Sunday to Remembrance Day in November each year and is observed in the UK and most parts of the Commonwealth. The purpose of this day is to remember all those who gave their lives in wars across history for Britain, and came about initially due to the slaughter of the Great War and the relief at its ending, at the 11th hour on the 11th day of the 11th month in 1918. There are services held in nearly every church or chapel around the country, as almost every single city, town and village in Great Britain has a war memorial to remember those from the parish who died in the two World Wars. The services are sometimes organised by the Royal British Legion, whose members are veterans of the armed forces and who are aided by the Poppy Appeal.
This service features a fairly standard procedure and can last anything from 15 minutes to an hour. The most moving part is the two minute silence (the exact length varies, but lasts for at least one minute) observed at 11am, at which point most of the country falls silent. This is most often preceded by the haunting notes of the Last Post Sounded by a bugler. The Sounding of Reveille usually signals the end of the silence, although the exact point of the playing of these is subject to variation. This possibly symbolises that life continues after death, as "reveille" is French for "rising" or "waking" (thanks to Mortice for this). At some point in the silence or service the following words are spoken:
They shall not grow old, as we that are left grow old:
Age shall not weary them, nor the years condemn.
At the going down of the sun and in the morning,
We will remember them.
There is also a national service held at the Cenotaph in London. The Queen and other members of the Royal Family attend and lay wreaths of poppies at the foot of the memorial. Poppies are important as they grew in their thousands on the battlefields of the Western Front during World War One, as described in the poem In Flanders Fields. They have become a symbol of the suffering and sacrifices of combatants in that war. There is also a march-past, by the Services and by the Royal British Legion, although the number of marchers in the latter division is sadly dwindling year by year.
The day serves as a time to reflect on the sacrifice others in the past made for us here and now, and is an important tradition that should forever continue. The wearing of poppies and attendance at a Remembrance Sunday service, although I never attend Church otherwise and am certainly not a Christian, is something I hope to continue for every remaining year of my life. It's the least we can do for those who suffered and died for us all.
The words spoken in the service are from Laurence Binyon's For The Fallen; thanks to spiregrain and Gritchka for this info.