The document discusses different types of combustion such as rapid combustion and spontaneous combustion. It defines combustion as a chemical reaction between a substance and oxygen that releases heat. A flame is described as the visible gaseous part of a fire caused by a highly exothermic reaction taking place in a thin zone. Explosions are reactions where a large amount of gas is liberated suddenly. It notes the disadvantages of burning fuels can include releasing carbon particles and gases like carbon monoxide, carbon dioxide, sulfur dioxide and nitrogen oxides which are dangerous or contribute to issues like global warming and acid rain.