From the attic it could flow into exterior walls or through the ceiling insulation and stain the ceiling finish. Nonuniform roof surface temperatures lead to ice dams. Since most ice dams form at the edge of the roof, there is obviously a heat source warming the roof elsewhere. This heat is primarily coming from the house. In rare instances solar heat gain may cause these temperature differences.
Conduction is heat energy traveling through a solid.
A good example of this is the heating of a cast iron frying pan. The heat moves from the bottom of the pan to the handle by conduction. If you put your hand above the frying pan, heat will reach it by the other two methods. The air right above the frying pan is heated and rises. This is heat transfer by convection .