What does that bark mean?

Here is some great advice from the folks at Dogster.com about interpreting your pups barks:

Baying means your dog is on the chase, whining means she's frustrated, howling means he's calling the pack, growling when playing means she's playing tough, growling when confronting someone means he's mad, and yipping means she's hurt.
 Listen to the message in each of your dog's subtle and distinct vocalizations. You really CAN hear your doggy talk!