Acid rain is a kinda dangerous phenomenon caused by us humans. Although when you call it acid rain, it sounds like something straight out of a horror movie that would dissolve anything including humans, it actually is nowhere near strong enough to accomplish such a feat.
"Acid rain is any kind of percipitation with high levels of nitric and sulfuric acids." This is caused by rain reacting with sulfur dioxide and nitrogen oxide gases turning it into an acidic percipitation.
The harmful effects of acid rain aren't exactly instantaneous but they are definitely there.
Acid rain massively accelerates the decay of man made structures and vehicles. Even statues which hold a significant historical value aren't exempted.
Plants are also affected as it cause trees to grow slower and sometimes just randomly die. This is due to leaves being damaged and the harmful residue left in the soil being then absorbed by the trees.
The "benefits" of acid rain is that it cleanses the air since those harmful gases can even cause not only major visibility impairments massively reducing the distance you can see but also some heart and lung disorders like asthma and bronchitis.
Acid rain ist just another side effect of us humans polluting our planet. There is no way to prevent acid rain in the near future as we'll continue to drive our cars and burn fossil fuels to power things releasing the harmful gases that'll eventual rain right back down onto us.