Y is the earth shaped like a sphere? - Computers & Internet

Actually it isn't, it is shaped like an oblate spheroid, and for the same reasons that a water droplet is that the same shape, gravity physical forces and surface tension on a very large scale.
Before you point out that isn't really telling you why materials behave in that way, no one actually knows the reasons why, they just know that when material condenses the forces are such that a sphere is created. You can see it with every material from water to molten metal.The forces between the molecules pull the molecules together in a spherical shape, distorted by gravity.

Because Gravity pulls equally in all directions. When the Earth was forming, it was entirely molten rock. And, since Gravity pulls equally in all directions, the Gravity of the Earth pulled the molten rock into a sphere.