I grew up in the coal mining region of East Tennessee. We used coal in a pot bellied stove. It was messy, smelly,and sooty, but the heat was great. When I got married, the coal mines had about all closed. We used a coal/wood heater with wood. The difference is in the grates. Both have firebrick. The wood grate simply has holes for air to flow through and ashes to drop through. A coal stove has to have a shaker grate and an opening for the coal cinders to shaken through.