Before the pitcher throws the ball, the catcher signals with his fingers what kind of pitch to throw. Pitchers switch between straight fastballs and slower cur

Before the pitcher throws the ball, the catcher signals with his fingers what kind of pitch to throw. Pitchers switch between straight fastballs and slower curveballs and a pitch called a change up that looks like a fastball delivery but comes across the plate slower. Obviously if the hitter knew what to expect he’d do a lot better. So the astros had a camera that was looking at the signs and feeding them to the dugout. Then when they knew that a good pitch to hit was coming, they’d make a banging sound. It’s not actually super sophisticated. You’re actually allowed to steal signs from like a runner on second — you’re not allowed to use a camera to do it.