Hosted by the National Institute of Standards and Technology (NIST), this article by W. Martin and W. Wiese introduces the basics of atomic structure and spectra. With regard to structure, there is an emphasis on terminology and notation. Topics of discussion include wavelengths, intensities, shapes of spectral lines, and LS coupling. Originally appearing in the Atomic, Molecular, and Optical Physics Handbook, edited by G.W.F. Drake, this online version of Atomic Spectroscopy contains internal links as well as external links to spectroscopic data.