A spectroscopic binary is a type of binary star system where two stars orbit each other closely, making them difficult to resolve visually. Instead, astronomers identify them by analyzing their light spectra. As the stars move, their light shifts due to the Doppler effect, causing changes in the wavelengths of light that can be measured. These shifts reveal the presence of two stars, even if they cannot be seen separately. By studying the spectra, scientists can determine the stars' velocities, masses, and orbital characteristics, contributing to our understanding of stellar evolution and the dynamics of binary star systems.