An intentional walk occurs when the defending team elects to walk a batter on purpose, putting him on first base instead of letting him try to hit. Intentional walks -- which count as a walk for the hitter and a walk allowed by the pitcher -- are an important strategy in the context of a game. They can be used to put a runner on first base, setting up a potential double play.
Intentional walks occur most frequently with an excellent hitter at the plate and a significantly worse hitter -- or a more favorable matchup for the pitcher -- on deck. Generally, intentional walks occur with no one on first base, but they can also occur -- very, very rarely -- with first base occupied.
Beginning in the 2017 season, teams no longer need to throw four balls in order to intentionally walk a batter. Rather, the manager can signal an intentional walk from the dugout at any point during a plate appearance, putting the batter on first base automatically.
History of the rule
Prior to the 2017 season, teams were not able to intentionally walk a batter without throwing four balls -- though only the fourth ball needed to be intentional in order for the walk to be scored as such.
For intentional walks, a catcher would typically stand upright -- by rule keeping both feet inside the catcher's box until the ball left the pitcher's hand -- so he could more easily receive a pitch far outside the strike zone. Of course, hitters were not prohibited from swinging at an intentional ball attempt and would occasionally do so if the pitch was thrown closer to the plate than the pitcher intended.
Watch: Yadier Molina draws an intentional walk.
In A Call
"free pass," "putting him on"