Thermal radiation is the transfer of heat energy by electromagnetic radiation - typically infrared, but visible or even shorter wavelengths for very hot bodies. The rate of radiative heat transfer varies as the difference of the fourth powers of the temperatures of two objects, and on the amount of surface area exposed, and on the emissivity of the surfaces. Emissivity, e , is a number between 0 and 1 which indicates how good a material is at emitting thermal radiation. Typically, dark rough surfaces have emissivities near 1, while silvery smooth surfaces have emissivities near 0. A is the area of the surface.
Convection is heat transfer caused by the diffusion and bulk movement of a heated gas or liquid.
The heat energy is effectively transferred at the same time as the matter moves. In forced convection the fluid movement is forced by an external influence, such as a fan or pump. The physics of convection can be very complex and is far outside the scope of an introductory Guide.