"smooth cloth". A strong, smooth cloth made from a plant. It is worn by many people in places that are hot. (See how you translated this in Ezekiel 9:2). God told the man dressed in linen to take coals from between the wheels of the throne and scatter them over the city of Jerusalem. This was a symbolic action that showed God's judgment against the city and that it would be destroyed.
Coals are the burned pieces of wood left over after a fire. They are black, but they glow red and orange when they are very hot. They are also called charcoal.