A firecracker is a small firework made to bang, not to paint the sky. You light a short paper string, step back, and a second later it blows up with a sharp crack. There is a flash, a smell of smoke, and then paper on the ground. People set them off at Chinese New Year, at weddings, and at temple days, because a loud bang is supposed to scare away bad luck — though actually a lot of people now just like the noise, and a lot of cities have banned them because they hurt ears, start fires, and frighten animals. A firework show in the sky is not the same thing: those are the pretty lights. Firecrackers are the little ones whose whole job is to shout. Older speakers may also call a lively child a firecracker, as a joke, but learners almost always meet the firework first.