Weathering breaks materialn down and erosion transports that broken down material. As an example, weathering breaks a mountain down into smaller rocks, and those smaller rocks can be transported by streams (erosion), but the streams cannot simply move the whole mountain.
Igneous Rock turns into a Sedimentary Rock using Weathering and Erosion. Weathering breaks down the rock into small sediments. Erosion takes the rock and send the sediments into another location, where they are deposited and then consolidated to form a sedimentary rock.