Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism. One can take light and split it up to its wavelength components to form a spectrum.
If you click the pictures below they provide more detail on what spectrographs can do.
How Can Spectroscopy Help Us?
Here's an answer
Spectroscopy, as stated before, is the interaction between matter and radiated energy. It can help us identify elements on the periodic table as well as be a powerful tool in astronomy. It can help identify elements within a star without really sending anyone into outer space.