Mostly, yeah. During the game, it's an extra set of eyes in the dugout, another guy who has full knowledge of the scouting reports and your own players, who can watch the game and say to the manager "this guy's slow to the plate, we should send the runner" or "this guy's a dead pull hitter, we might want to shift the center fielder more towards left center" and stuff like that, a guy off whom the manager can bounce ideas like "what are your thoughts on a double steal here?" or "what do you think about pinch hitting this guy for that guy?", that sort of thing. Off the field, as you said, the bench coach will usually be responsible for some facet of instruction: on Lou's full staff, Sinatro was responsible for instructing the catchers, Trammell for working with the infielders and Quade for working with the outfielders. Those three - infield, outfield, catching - will usually be split somewhere among the bench and two base coaches. The bench coach is also responsible for coordinating daily practices, stretching and drills, both in the spring and during the regular season.