This is a betting line used only for ice hockey games in which a point spread is applied to the favorite and underdog with the odds adjusting to that point spread and the relative strength of the team. Typically, the underdog receives +1.5 goals with the favorite getting -1.5 goals, which means for the underdog to win the bet they must not lose by 2 or more goals and for the favorite to win they must win by at least 2 goals. Additional puck lines, such as +/- 2.5 are also generally offered at sportsbooks.
For example, if the Edmonton Oilers are playing the Chicago Blackhawks and the puck line for the Blackhawks is -1.5/+185 it means that if you bet $100 on the Blackhawks puck line and they win the game 5-2 you will win $285 ($185 + your original $100).
Puck Line is so named due to exclusive use in ice hockey (a puck is the object teams try to score, synonymous with a ball in other sports). The puck line is similar to the run line used in baseball.