Convection refers to the mode of heat transfer encountered between a surface and a flowing fluid. It can be thought of as a combination of conduction and advection.

Convection = Conduction + Advection

The working equation for convection heat transfer is

Q_dot = hA(T_surf - T_fluid),

where Q_dot is the rate of heat transfer, h is the convection heat transfer coefficient and A is the surface area.

Of course the whole trick to doing a convection calculation is finding h (and sometimes even T_surf - T_fluid) but that is the purpose of this map.