pretty much this.. a candle will give off the same amount of heat where ever it is, but if you surround it in mass - especially materials that absorb large amounts of heat, you can gimp how quickly the heat 'escapes' hence why there are 2x ceramic pots plus a fuck ton of metal. it keeps the heat closer to the ground where you are for longer. it isnt gonna heat a whole house though, as i said its the same amount of heat..
Australia