Thermal radiation definition
Thermal radiation is the transfer of thermal energy from one place to another by means of electromagnetic radiation.
All objects radiate thermal energy in all directions.
Objects at room temperature radiate mainly infrared radiation.
The sun radiates lots of visible light.
Hotter objects like a glowing piece of wood in a fire radiate more energy than colder objects like ice.
Unlike conduction and convection, thermal radiation does not require a material to transfer energy or to move. Objects can radiate energy across a vacuum.
When you heat a stone in a fire and then take it out, the stone will radiate. Getting close to the stone you will feel this radiation as warmth.