Canadian Involvement in Afghanistan

I don't have much knowledge on the war in Afghanistan and to be honest don't pay much attention to it at all. The war is supposed to be a "War on Terrorism", but it does'nt seem that it is that way at all. I can't really justify Canadian troops being there because I don't know the role they are playing. Are they actually fighting the Taliban or trying to stabilize the government and destroy Al Queda forces? The death of Canadian soldiers is apalling and uncalled for.