I've looked at the glossary and read the definitions but I'm still a little foggy. Can someone clarify for me the difference between a "mystery" and a "puzzle"?

Mystery relates to the letterbox's location: where is it? It's a mystery.

Puzzle relates to the clue: it's not going to be straightforward directions to the box, you have to solve something first.

So a box can have a mystery location, which yes usually means you have to figure out a puzzle to determine where the box is. But, for a puzzle box that isn't a mystery location, you can also have a location, say a particular park, and still need to solve a puzzle for the directions on how to get to the box.

As clear as mud?

A mystery does not give you a specific starting point: you have to figure that out.

A puzzle does not give you a specific ending point: you have to figure that out.

Kelsung

Mystery: http://www.atlasquest.com/showinfo.html?gBoxId=215729: because one must figure out where to start looking.

Puzzle: You know where to start looking but need to solve a puzzle to find the box: http://www.atlasquest.com/boxes/clue/?gBoxId=212593

Puzzle Mystery: You have to figure out where to go, and then solve a puzzle to figure out what to do.

Oops. Puzzle Mystery or Mystery Puzzle: http://www.atlasquest.com/boxes/clue/?gBoxId=198220

Thanks everyone. Very puzzling still but I think I've got it.

Mysteriously puzzling.