What is heat transfer? Write its modes. In which mode,medium is not required?

(N/A) Heat transfer is the process of movement of thermal energy from a body at a higher temperature to a body at a lower temperature due to the temperature difference between them.
There are three modes of heat transfer:
$1$. Conduction: Heat transfer through a solid medium without the actual movement of particles.
$2$. Convection: Heat transfer through fluids (liquids and gases) involving the actual movement of particles.
$3$. Radiation: Heat transfer through electromagnetic waves.
Radiation is the mode of heat transfer that does not require any material medium for propagation.