Some people say that the splitter and the forkball are cousins. Well, yes and no. The one thing they have in common is that you throw both pitches with the same motion (and the same arm speed) as the fast ball. But the real difference between them is the grip.
The forkball is gripped with the index and middle fingers spread very wide apart so that they are on the sides of the ball—and it ain’t easy if you have a small hand. The splitter, or split-finger fast ball, is easier if you don’t have a large hand, because the spread isn’t that wide. You grip as for a two-seam fast ball, but with the fingers just on either side of the seams. There are some pitchers who can throw both these pitches—think Jose Contreras, for example. He uses both, and when they’re working the batters have conniption fits trying to hit either pitch.
The uncomfortable thing about the splitter is that if you miss the target, throw that pitch too low, it’s likely to end up in the dirt. Or if it doesn’t behave the way it should, whoops, double off the right field wall or some such. 8)