As a conceptual model of the mysterious phenomenon of heat transfer by radiation one may think of heat transfer by conduction and as a model of heat transfer by conduction one may think of the transfer of water in a system of lakes at different altitudes, with altitude corresponding to temperature.
In the lake system there is one-way flow of water from higher to lower altitude driven by hydrostatic pressure. Conduction transfers heat energy from higher to lower temperature. Radiation transfers heat energy from higher to lower temperature.
The flow of water, or heat energy, can be seen to be governed by a 2nd law stating that Nature always seeks to decrease difference in water level, or temperature.
Why does Nature have this tendency to decrease difference, which by the way Nature shares with social-democrats in Sweden and elsewhere? Why is Nature not seeking instead to increase difference, like a good old capitalistic system is supposed to do?
Because, in a certain sense Nature is simple-minded and it is easy for a simple mind to simply decrease difference by the simple process of mixing, which requires no distinction. Just stir and mix.
On the other hand, the reverse process of increasing difference by unmixing is difficult because it requires distinction.
In short: decreasing difference is simple and stable and can be easily be accomplished by a natural simple process, while increasing difference is difficult and potentially unstable and thus requires some form of intelligence, or at least some process for separation or selection.
The above model can be read as a conceptual version of my analysis of radiative heat transfer in Mathematical Physics of Blackbody Radiation and of the 2nd law of thermodynamics in Computational Thermodynamics.