Baseball, by the Rules

Pitcher Hunter Dobbins of the Boston Red Sox rubs his spikes on the cleat-cleaner on the back of the pitching mound, prior to a plate appearance starting against the Minnesota Twins.
A Plate Appearance Starts
No matter what else is happening in a game, when a batter comes up to the plate to start a place appearance, the count is always 0-0: 0 balls and 0 strikes.
During the lead up to the first pitch of the plate appearance, the pitch timer starts, counting down from 15 seconds. The batter must be in the batter’s box and ready to swing with at least 8 seconds left on the clock. If not, the umpire calls an automatic strike. Similarly, the pitcher must start their pitching motion before the clock runs out. If not, the umpire calls an automatic ball. The umpire does have the authority to pause the pitch timer in special circumstances1.