What is spontaneos and explosive combustion.please explain clearly and urgently

spontaneous reactions are those which take place at the same instant ie the Spontaneous combustion or spontaneous ignition is a type of combustion which occurs by self-heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self heating which rapidly accelerates to high temperatures) and finally, ignition.

Spontaneous combustion or spontaneous ignition is a type of combustion which occurs by self-heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self heating which rapidly accelerates to high temperatures) and finally, ignition.The speed of the reaction is what distinguishes an explosive reaction from an ordinary combustion reaction. Unless the reaction occurs very rapidly, the thermally expanding gases will be moderately dissipated in the medium, with no large differential in pressure and there will be no explosion..... thanks