Spectra refers to the range of wavelengths or frequencies of electromagnetic radiation emitted or absorbed by a substance, which can provide valuable information about its composition, structure, and behavior. Spectroscopy is the scientific study of these spectra and is used in various fields such as chemistry, physics, astronomy, and biology. Spectra can be obtained through methods such as absorption spectroscopy, emission spectroscopy, and fluorescence spectroscopy, and are analyzed to identify elements or compounds present in a sample, measure concentrations, and study energy levels and transitions within atoms and molecules. Spectra are also used in fields such as remote sensing, environmental monitoring, and medical diagnostics.