A boy in an orange 'Spring Hill' ball team uniform, pitching the ball.
A boy pitches the ball.
pitching is just the present tense of pitches
A boy pitches the ball is a simplification and rephrasing of A boy in an orange 'Spring Hill' ball team uniform, pitching the ball.
Sentence 1 is about a boy pitching a ball, and sentence 2 is also about a boy pitching a ball.