Aravind,
We generally use the two terms interchangeably. Although that might not be technically correct at the physics level, all of the power consumed by the device must be dissipated as heat. Your design has to dissipate all of the power consumed sufficiently to maintain a case or junction temperature as specified by the datasheet.
Is your concern over the distinction of the two terms, or are looking for hardware design advice for thermal dissipation?
Regards,
RandyP