Red Nose Day is the main fundraising event of Comic Relief. Comic Relief itself started in 1985; it was launched by comedy scriptwriter Richard Curtis and comedian Lennie Henry, who like several other celebrities at that time (notably Bob Geldof) were anxious to help with the famine in Ethiopia. However, the original idea of using entertainment to raise money for the famine victims came from Jane Tewson, a charity worker in Africa.
Comic Relief started around Christmas that year, and then on 5 February 1988 the first Red Nose Day event was launched. It was organised by Wendy Crossman of Comic Relief, and the event was held by the BBC as it still is. Nowadays Red Nose Day is usually held later, in the second or third week of March. Most of the money is raised through the TV programmes where people phone in their donations, but there are also fundraising events held all over the country on the same day.
You can find out more about Red Nose Day and its aims here.