"Swing" is the gap between a team's highest and lowest ever rating within the selected range - a rough gauge of how volatile a team's history has been versus how consistent. Peak/trough use the actual per-game rating, not the smoothed chart line.
Highest-ever ratings
#
Team
Elo
Date
Lowest-ever ratings
#
Team
Elo
Date
This ranks every individual game ever played (any team), so one team can occupy several of the top 10 if their history is unusually dominant (or several of the bottom 10 if it's been rough) - it isn't limited to one entry per team like the table above.