Many kids aren’t sure how to grip the baseball in certain situations, so let’s talk about it… A two-seam grip is mainly used when pitching, while a four-seam grip is used at all times by all position players and sometimes as a pitcher. The reason a pitcher uses a two-seam grip is to create more movement with their pitch. This is caused by the lack of friction against the air from only having two seams per rotation “catching” air, which allows gravity to work faster to pull the ball towards the ground. When using a four-seam grip, there are four seams “catching” the air per rotation working against gravity to keep the ball from dropping. When watching a strong-armed outfielder throw with a four-seam grip, the baseball will look like it is actually rising! If he threw the same way using a two-seam grip, it would have less of a chance to carry the same distance and it would tail towards his arm side. Pitchers will use a four-seam grip when throwing a high fastball when ahead in the count or when they are struggling to find the strike zone with their two-seam fastball.
I hope this helps! If you have any questions, post them below.