Take into account that velocity is a vector quantity, so a change of it can be a change in magnitude (like in a vehicle which moves in a straight line an accelerates from 25 mph to 40 mph), or direction (like a vehicle describing a circular motion at 25 mph which receive a centripetal acceleration), or even a combination of both.
This is called heat transfer. Heat transfer is the process in which energy flows from a matter that is higher in heat to a matter that is cooler, until the two matters reach the same temperature.
