These gases rise into the air from chimneys or vehicle exhausts. These gases can fall as dry deposits often close to the factory. People can find dusty deposits on washing hung out to dry. The pollution can also mix with rain clouds. The clouds may be carried long distances in weather systems, so the rain can fall in countries a long way from the factory making the pollution.
Acid rain is known as a wet deposit.
The rainwater runs off the land and collects in lakes and rivers where fish can be killed. Trees that intercept the rainwater can also be killed.