Understanding the surface of our Earth is difficult without first understanding the interior, or inside of the Earth. This is because everything that is on the outside, has been formed by the enormous heat, and forces that exist on the inside.
Continents have been created, mountains raised, only to later be lowered, hot magma has been pushed to the surface, as older rock is re-heated, turning back into magma, and so on.
Without the many powerful forces going on inside of the Earth, the surface of our planet would look much more like the Moon. It would be a dead world geologically. Thus, these forces help to not only form the Earth, but also to repair, and maintain it.