Sparks are the bright glows due to tiny masses of matter heated to extremely high temperature. It could be a small amount of air in between two electrodes held at high enough electrical potential difference so as to heat it by the current, it could be flying mass of specks of metal particles in a sparkler heated by chemical burning, it could be a flying splinter resulting from the striking of two metallic bodies against each other, or it could be a small sized particle separated from a large body of stone locally heated by friction with another object. In all these cases and more, one observes a flying spark glowing bright.
