What is the box connecting the exhaust pipe? Why is it leaking? Find a solution

Hello, this is the muffler. Usually, this thing has a drain, and that is a three-way catalyst, which is responsible for automobile exhaust emissions. In which box can your vehicle exhaust meet the national emission standards through chemical action, mainly the reduction of particulate matter and carbon dioxide emissions. The exhaust temperature of the engine is about 800 degrees, and the three-way catalyst will produce water vapor where it is hot and cold alternately. There is water vapor under the car, which has nothing to do with turning on the air conditioner. If the air conditioner is turned on, which drain pipe is under the car? Hello, is this the last section of the exhaust pipe? This function is silence. Dropping water is normal, because the product of gasoline combustion is water. @20 19