A base on balls (BB), better known as a walk,occurs in baseball when a batter receives four pitches during a plate appearance that the umpire calls balls, and is in turn awarded first base without the possibility of being called out. The base on balls is defined in Section 2.00 of baseball's Official Rules, and further detail is given in 6.08(a). Despite being known as a "walk", it is considered a faux pas for a professional player to actually walk to first base; the batter-runner and any advancing runners normally jog on such a play.
The term "base on balls" distinguishes a walk from the other manners in which a batter can be awarded first base without liability to be put out (e.g., hit by pitch (HBP), catcher's interference). Though a base on balls, catcher's interference, or a batter hit by a pitched ball all result in the batter (and possibly runners on base) being awarded a base, the term "walk" usually refers only to a base on balls, and not the other methods of reaching base without the bat touching the ball. An important difference is that for a hit batter or catcher's interference, the ball is dead and no one may advance unless forced; the ball is live after a walk (see below for details).