Today is Armistice Day 11th November 2011.
A two minute silence is observed at 11am on 11th day of the 11th month because this is when the Great War, or World War 1, came to end in 1918.
The first two minute silence was held on 11 November 1919, when King George V asked the public to observe a silence at 11am.
This was one year after the end of World War 1.
Poppies are used because they grew on the battle fields after world war 1.
Armistice day and remembrance day (1st Sunday following armistice day) are not just for remembering all the fallen service men and women of world war 1, but all the wars since then.