If we find any simpler sources of the very basic information, we'll link to them from this answer. The U.S. Environmental Protection Agency's Web sites has several links to this kind of information. Click here to go to the topic home page. They are both weak acids. Stronger acids, such as the acid in a car battery, can be extremely dangerous because they can burn you.
Acid rain refers to any precipitation, rain or snow, that's more acid than ordinary rain or snow.
Once they are in the air, these substances can combine with water vapor to form weak acids that become part of rain or snow. In some parts of the world, the lakes are in limestone, which neutralizes acid from rain. But in other areas, including parts of the northeastern United States and eastern Canada, the lakes are in granite, which does not weaken the acid. While the acid in such lakes is relatively weak, it is enough to kill fish, salamanders, frogs and many bacteria in lakes. Tiny water plants might also die.