Inside any radiator, there is hot water entering the bottom and leaving at the top.
Thermal energy from this water conducts through the metal to its outside surfaces.
This heats the air around the radiator which then rises (convection) and circulates round the room.
Only a small amount of heat energy is radiated as 'IR' (infra-red)
These heaters have electrical heating elements inside that glow red hot.
Air around them is heated.
Then rises out of a grille near the top.
And then circulates around the room.
Cold air is drawn along the floor and enters the heater through a grille in its base.