Idealized radiation, produced by an object which is a perfect absorber and emitter of radiation.
Any object surface can radiate heat to and receive heat from outside, if an object can absorb all the incident radiation, regardless of the frequencies and directions, this object is called Black Body. A ball cavity with a small hole can be regarded as a black body, since any radiation entering the ball cavity can only reflect inside it, thus totally absorbed.
light or other electromagnetic radiation emitted due to heat by a solid, liquid or dense gas, with no color of its own (hence "black"). Distinguished by a continuous distribution of spectral color, with its peak of emission shifting towards shorter wavelengths as the temperature increases--e.g. infra-red for a warm hand, red for a hot iron bar, yellow for the glowing filament in a lightbulb.
Black body radiation is the radiation emitted by a perfect black body, i.e., a body which absorbs all radiation incident on it and reflects none. The wavelength dependence of the radiated energy density (energy per unit volume per unit wavelength range) is given by the Planck formula where is the wavelength, is Planck's constant, is the speed of light, is the Boltzmann constant, and is the temperature.
Radiation emitted by a hypothetical perfect radiator. The spectrum is continuous, and the wavelength of maximum emission depends only on the body's temperature.
Radiation characteristic of a body that perfectly absorbs all the radiation falling on it.