Short answers, pulled from the story.
Erosion is the action of surface processes such as water flow or wind that remove soil, rock, or dissolved material from one location on the Earth's crust and transport it to another location where it is deposited. It is distinct from weathering, which involves no movement. Eroded material may travel just a few millimetres or for thousands of kilometres.
The main agents of erosion include rainfall, bedrock wear in rivers, coastal erosion by waves, glacial plucking and abrasion, areal flooding, wind abrasion, groundwater processes, and mass movement such as landslides and debris flows. Physical erosion proceeds fastest on steeply sloping surfaces.
Human activities have increased the global rate of soil erosion by 10 to 40 times. At agriculture sites in the Appalachian Mountains, intensive farming has caused erosion at up to 100 times the natural rate for the region. Water and wind erosion together cause about 84 percent of the world's degraded land.
Rainfall and surface runoff produce four main types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion. Splash erosion is the first and least severe stage, and gully erosion is the most severe. A gully is distinguished from a rill by a critical cross-sectional area of at least one square foot.
Glaciers erode mainly through three processes: abrasion or scouring, plucking, and ice thrusting. In abrasion, debris in the basal ice scrapes along the bed and polishes and gouges the underlying rock. Glacial erosion also limits mountain height, an effect known as the glacial buzzsaw, with peak-to-snow-line relief generally confined to less than 1500 metres.
Erosion removes and transports soil, rock, or dissolved material from its original location, while deposition is the arrival and emplacement of that material at a new location. Deposition follows the transport of eroded materials. On a river bend, the slower-moving side builds deposits while the faster-moving side erodes away.
Wind erosion has two primary varieties: deflation, where wind picks up and carries away loose particles, and abrasion, where surfaces are worn down by airborne particles. Saltation is responsible for 50 to 70 percent of wind erosion, followed by suspension at 30 to 40 percent and surface creep at 5 to 25 percent.