Dawn,
A "shotgun" is a form of chip trading...kind of like a chip trade grab-bag!

Tom wants to trade 2 Canadian chips per envelope, $1 denomination (I think), slightly used (or better) condition, and a maximum of 5 people will be involved (Tom plus 4 other participants).

Each participant will address an envelope to each of the other 4 participants. They will put 2 $1 Canadian chips in each envelope, and will mail them. Then they wait to receive their chips from the other 4 participants.

Hope that is a little clearer than mud!