If you see a cricket bat side-ways, you will notice a curve below the bottom half of the bat. What's the purpose of that curve and I have seen different curves in different bats. How does this curve effect in batting??
The curve of a cricket bat has several functions. First, it balances the bat, especially larger bats, by bringing the mass that's behind the "sweet spot" forward relative to the hands; a straight bat of a professional size and weight would have more mass behind the line indicated by the handle through the bat, and would be harder to maneuver. Second, the curve enlarges this "sweet spot" by increasing the surface area that's close enough to the center of mass to gain an advantage, and also by allowing the bat to "trampoline" the ball when hit towards the tip.
Finally, it allows for a bit of finesse in various shots. The curved tip allows the batsman to more easily "pull" the ball with a side swing, hitting toward the opposite side of the field as would be expected (a right-handed batsman will typically "push" the ball to his right, much like a RHB in baseball will tend to do the same). It also allows for a better defensive swing (a swing made more to block). Such swings typically lead with the hands and the bat ends up angled downward and backward at impact. In this stance, the curve presents a steeper angle to the ball at impact, so that the ball will bounce downward more strongly instead of rearward, hopefully keeping it away from the wickets and keeper.