  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.
