This is a hot, glowing solid , so the light bulb produces a continuous spectrum. Emission and absorption line spectra are made by electrons changing orbital levels. Electrons orbit the nucleus of the atom in various orbital levels. There are rules that determine whether the electrons can be in certain levels, such as how much energy the electrons have and how many electrons are already in that level. Because of the pull of gravity, it takes less energy to go down than up, which is why water flows downhill.
Electrons are the same way.
They will orbit an atom at the lowest energy state that they can get away with. Occasionally extra energy, such as radiation, will connect with the electon and it will absorb this energy. The electron will get excited and jump up to a higher orbital level. Since the electron absorbed the energy, that wavelength is no longer seen in the continuous spectrum. Instead there is a dark gap where that wavelength would have been, thus causing an absorption spectrum .