Zeppelin or balloon?

So what is the difference between a balloon, dirigible or Zeppelin?

Thanks to http://www.airships.net/dirigible for the answer:

"A dirigible is any lighter-than-air craft that is both powered and steerable (as opposed to free floating, like a balloon).  Blimps like the Goodyear blimp, rigid airships like the Hindenburg, and semi-rigid airships like the Zeppelin NT are all dirigibles.

The word “dirigible” is often associated with large rigid airships, but the term does not come from the word “rigid,” but rather the French verb “diriger” (“to steer”)."

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