We review the motivation for the axion as a solution of the strong
CP puzzle and as a candidate for cold dark matter. Then we discuss
benchmark axion models and present their predictions concerning
axion couplings to the Standard Model and
axion dark matter abundance.
Finally, we give an overview on the discovery potential of current and planned
axion experiments, reaching from axion dark matter direct detection,
over searches for solar axions, to direct production and detection
of axions in the laboratory.