What does E pluribus unum mean?

E pluribus unum is the motto on the Great Seal of the United States. It is also on passports. In 1782 it was adopted by an Act of Congress.

So what does it mean? I'm sure that I learned this in children's books, but I've forgotten since then. E pluribus unum is Latin for out of many, one. It usually appears with all capital letters. It suggests that out of many states, there is a single nation.