Cut and pasted from Wikipedia:
"Do They Know It's Christmas?" is a song written by Bob Geldof and Midge Ure in 1984 to raise money for relief of the 1983–1985 famine in Ethiopia. The original version was produced by Midge Ure and released by Band Aid on 29 November 1984.
In October 1984, a BBC report by Michael Buerk was aired in the UK, which highlighted the famine that had hit the people of Ethiopia. Irish singer Bob Geldof saw the report and wanted to raise money. He called Midge Ure from Ultravox and together they quickly co-wrote the song, "Do They Know It's Christmas?".
Geldof kept a November appointment with BBC Radio 1 DJ Richard Skinner to appear on his show, but instead of discussing his new album (the original reason for his booking), he used his airtime to publicise the idea for the charity single, so by the time the musicians were recruited there was intense media interest in the subject. Geldof put together a group called Band Aid, consisting of leading British and Irish musicians who were among the most popular of the era. On 25 November 1984, the song was recorded at Sarm West Studios in Notting Hill, London, and was released four days later.
The 1984 original became the biggest selling single in UK Singles Chart history, selling a million copies in the first week alone. It stayed at Number 1 for five weeks, becoming Christmas number one, and has sold 3.69 million copies domestically. Worldwide, the single had sold 11.8 million copies by 1989.
Following the release of "Do They Know It's Christmas?" in December 1984 and record sales in aid of famine relief, Geldof then set his sights on staging a huge concert, 1985's Live Aid, to raise further funds.