A cricket ball is a rounded hard cork stuff wrapped and stitched with leather pair to make it a perfect round cricket ball.
Initially The cricket was played only with the red balls but now in modern days to make it more attractive and competitive balls colour have been changed to red, white and pink.
While in the early days of cricket ball was used only by the fast bowlers to bowl out the batsman, it was in seventies, bowlers got the mastery of seaming and swinging the cricket ball to make it more lethal weapon for bowlers, as the game progress the reverse swing bowling invented by some of the bowlers. In todays cricket if a bowler don’t know how to swing or seam the cricket ball, his career as a bowler would not last long.
Swing the ball is purely a technology in which cricket ball deviates its path either inside or outside when throws from bowler hand to batsman, Ideally it should move in a straight line towards batsman but here if a bowler knows the art of swinging he can fool the batsman through sudden deviation of ball.
Swinging of cricket ball depends upon some factors like
Sewing of cricket ball
Polish on the ball
Wear and tear of the ball
Angle of delivery of the ball
Air direction in the cricket ground
Bowlers speed etc.
When ball is shining new on both sides then the swinging of the ball is achieved through proper use of seam of the ball, when a bowler wants to deviate the ball outside then seam position is tilted a bit towards the slip so as to create a angle of the ball towards slip while it hit the ground.
When a bowler wants to achieve opposite effects ie inswing from a new ball the seam position tilted a bit towards batsman.
When cricket ball is old enough to not producing swing effect from seam then one sided tear and wear effect of the ball is used to get swing.
In the process bowlers used to shine one side of the ball with their saliva or sweat and other side is exposed to normal wear and tear thus one side is shinier and other side is relatively rough, when a bowler deliver the ball in the air, there would be pressure gradient on both side of the ball as the air passes easily through the shinier side and got some resistance while passing the rough side of the ball hence as a resultant ball will deflected towards the rough side of the ball while throws with a good speed by the bowler.
Using this phenomenon a bowler can deflect or swing the ball in the air.