There are three types of spectra :
Continuous Spectra :
This is the separated wavelengths of white light, produced as a continuous spectra, a like a rainbow
Absorption Spectra :
If the EM light has had to pass through a gas cloud to get to the spectrometer, then it will have some wavelengths missing. Atoms of the gaseous elements that make up the gas cloud will absorb very specific wavelengths of light. This gives us insight into the element makeup of a star.
Emission Spectra :
Once the atoms of the gaseous elements are energised, the excited electron will quickly return to a lower energy level and in doing so will emit specific frequencies of light, producing a characteristic colour for that element.