The insolation is made up of energy transmitted directly through the atmosphere and scattered energy.
Insolation is the amount of solar radiation that reaches the earth’s surface through short waves.
The earth also radiates heat energy like all other hot object.
This is known as terrestrial radiation.
The annual mean temperature on the surface of the earth is always constant.
It has been possible because of the balance between insolation and terrestrial radiation. This balance is termed as a heat budget of the earth.
Although the earth as a whole, maintains balance between incoming solar radiation and outgoing terrestrial radiation. But this is not true what we observe at different latitudes.
The amount of insolation received is directly related to latitudes.
In the tropical region the amount of insolation is higher than the amount of terrestrial radiation.
Hence it is a region of surplus heat.
In the Polar Regions the heat gain is less than the heat loss.
Hence it is a region of deficit heat.
Thus the insolation creates an imbalance of heat at different latitudes.
This is being nullified to some extent by winds and ocean currents, which transfer heat from surplus heat regions to deficit heat regions.
This is commonly known as latitudinal heat balance.