Weathering. Weathering is what breaks down a rock. is many different ways that weathering can occur in many different places and times, for example when there is a crack in a rock and a plant starts to grow inside the crack the rock will crack even more and eventually break that is a form of weathering.
Erosion.Erosion is what picks up broken down rock and sediment and brings it to another place. Erosion works with weathering after weathering breaks the rock into sediment then erosion comes in and picks up. One example is when a glacier moves across land it is picking up material and taking it.
Deposition.Deposition is part of the W.E.D. group too and its job is the last job, droping the sediment after erosion carries it. Deposition drops the sediment to a new destination. for example when a Delta is made the sediment is flowing down a river and then it all drops and creates a delta.