* Gravity's Pull: Gravity pulls everything towards the center of a planet. This pull is equal in all directions.

* Early Stages: When planets form from dust and gas, these particles clump together due to gravity. As the clumps grow larger, their gravitational pull becomes stronger.

* Even Distribution: This stronger gravity pulls material from all directions, resulting in a more even distribution of mass.

* Spherical Shape: The most efficient way to distribute mass evenly under the influence of gravity is a sphere. Imagine trying to build a structure out of sand. It would naturally form a mound, and a sphere is the most stable and efficient way to contain that sand.

It's not a perfect sphere: Planets are not perfectly spherical. They might have bulges at their equators due to their rotation, or slight distortions caused by the gravitational influence of other objects.

Let me know if you have any other questions!