  Time-dependent density-functional theory (TDDFT) is a formally exact approach
to the time-dependent electronic many-body problem which is widely used for
calculating excitation energies. We present a survey of the fundamental
framework, practical aspects, and applications of TDDFT. This paper is mainly
intended for non-experts (students or researchers in other areas) who would
like to learn about the present state of TDDFT without going too deeply into
formal details.
