Weathering Breaks, Erosion Takes
The fundamental difference between weathering and erosion is that weathering is the process of breaking down rocks and soil, while erosion is the process that moves those broken pieces. Weathering creates the sediment, and erosion transports it.
An Example on a Mountainside
Imagine a large boulder. When water seeps into a crack, freezes, and expands, it breaks a piece of the boulder off. This breaking process is weathering. Then, when wind or a stream of water carries that broken piece down the mountain, that movement is erosion.