This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
Checked exceptions are have to be handled at compile time, unchecked exceptions need to be handled at runtime. Checked exceptions subclass java.lang.Exception, unchecked exceptions subclass java.lang.RuntimeException. Here this can be a little confusing, since RuntimeException also extends Exception. The thinking is that unchecked exceptions are supposed to be more trivial (though this is not necessarily how it works in practice).