Bonfire Night

Before I moved to Scotland I had never heard of Guy Fawkes night. Still not sure that I fully understand the whole reason behind it. I know the history, but what aspect of this historical event are people celebrating? Is it the attempted terrorist attack or the foiling of the attempted terrorist attack? Do people understand why they are celebrating? And why do people start setting off fireworks weeks before the actual night? I have never really paid much attention to Bonfire night, but decided to document this event this year.