The informal economy of China is when people buy and sell goods, services, and even labor outside of the formal economy. This means that they are not taxed, don't have to follow regulations, and often get paid less than the people in the formal economy. However, it also means that these people may not have the security and benefits that those in the formal economy have. China's informal economy is very big because many people are very poor and don't have access to the employment opportunities in the formal economy. This means that the informal economy is an important way for people to get by and make a living.