Original image by MapleDude.Ca
November 11 is a memorial day in Canada, United Kingdom, Australia and other countries of Commonwealth of Nations (former territories of the British Empire). This day is called Remembrance Day or Poppy Day (“Armistice Day” before that).
On that day these countries recall members of armed forces who have died in the line of duty during first World War and other conflicts.
A red flower people wear on that day is called “Red Remembrance Poppy”. This day is known in many countries as Veterans day (Independence Day in Poland, Remembrance of the Dead in Netherlands etc.) and it’s often a public holiday.