What is the difference between erosion and deposition?

Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water or ice, by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion). 

Deposition, also known as sedimentation, is the geological process whereby material is added to a landform. This is the process by which wind, water or ice create a sediment deposit, through the laying down of granular material that has been eroded and transported from another geographical location. 

Deposition occurs when the forces responsible for sediment transportation are no longer sufficient to overcome the forces of particle weight and friction, which resist motion. Deposition can also refer to the build up of a sediment from organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which has induced chemical processes (diagenesis) to deposit further calcium carbonate.