The Chinese invented fireworks in the 7th century, purportedly in the ancient city of Luòyáng (洛阳) during the Han Dynasty (汉朝; Hàn Cháo) by cramming saltpeter, sulphur and charcoal into bamboo tubes. Fireworks were used to pray for happiness and prosperity as well as to scare away evil spirits. Two thousand odd years later, the novelty hasn't by any means worn off. Fireworks are a very common part of Chinese life, often used at weddings and other celebrations. In fact, I hear them almost weekly from my apartment in Xiamen (I think originating at a nearby restaurant which hosts wedding parties).
Nothing, however, compares to the proliferation of pyrotechnics during the Chinese New Year. In addition to fireworks displays, it seems almost every Chinese person feels compelled to shoot off firecrackers which end up littering and sometimes literally covering the streets. I actually think there must be a Chinese law that requires each member of China's 1.3 + billion population to at least shoot off a few, cheap firecrackers. According to the Guardian, New Year celebration fireworks have caused a dangerous rise in Beijing pollution (which is bad enough under normal circumstances).
While the constant month-long ruckus of firecrackers going off all around you can be annoying, some of the fireworks displays can be spectacular. For those of us that aren't in China, here's a video of a fireworks display in Hong Kong's scenic Victoria Harbor.