Period is the time taken by a wave to repeat itself at a given point in space.
Wavelength is the distance in which a wave repeats itself at a given point in time. In case of light waves, which do not require any material medium to propagate, Amplitude is defined as the maximum value of the electric field. They differ in their wavelength. A Black body is defined to be a perfect absorber and emitter of radiation. A Black body curve looks like Fig. 2.9 on page 52 of Chaisson and McMillan.