Cricket and baseball evolved from the same roots; a game called Cats & Dogs.
In baseball, you have a pitcher, who hurls the ball at the batter at high speed. The ball, however, flies through the air.
In cricket, the bowler (pitcher) does the same, except the ball hits the ground before the batter can hit it.
The difference is that you have "Fast" bowlers (80-95mph), "Medium pace" bowlers (75 - 85 mph), and "Spinners" (50-60 mph).
The spinner manipulates the ball so that, when the ball hits the ground, it will spin to the left, or right, or straight up. Spinners rely on guile, flight, and disguising the delivery, in order to confuse the batter.
Get a load of this guy (an Ozzie) who was probably one of the best in history: