Hey one of you smarties answer my question on page 5, so I can be a more educated fan...please.
The 1-3-1 is a forechecking system where the first skater in pressures the puck then 3 skaters go in to support the forecheck. The main goal is to outnumber your opponent and cause turnovers.
This is a dangerous system as it has a tendency to leave your defense exposed, and most coaches go with 2-1-2. (2 skaters pressure the puck, 1 for support, 2 back on defense.)