Erosion is a process where natural forces like water, wind, ice, and gravity wear away rocks and soil. It is a geological process, and part of the rock cycle. Erosion occurs at the Earth's surface, and has no effect on the Earth's mantle and core.
Most of the energy that makes erosion happen is provided by the Sun. The Sun's energy causes the movement of water and ice in the water cycle and the movement of air to create wind.