Weathering is where rocks and minerals are broken down into smaller and smaller pieces. Extreme heat and cold, water, and ice can all cause weathering. Water wears away rocks, and can dissolve them. When water seeps into cracks on a rock, it freezes, and gets bigger, causing the rock to push out.
Erosion is simply the transportation of weathered, or broken down, materials. Wind and water can erode, and so can movements from the earth. Water can carry the broken down rocks, and so can wind. A landslide is when lots of materials are carried down a steep hill by gravity. A mudslide is when water makes the side of a hill heavy, and carries it downward. Slumps are when a large amount of rock or dirt, or other sediments, fall. All the material in a slump always comes down at once, where a landslide can have many rocks tumbling down at different times. When the earth moves slowly, it's called a creep.
Deposition is when sediment, and broken down substances are deposited, or layed down somewhere. This can happen in a river when the water slows and creates a new bank, or delta. When wind slows down it can also drop sediment.