Gamma-ray binaries

Gamma-ray binaries are a subclass of high-mass binary systems whose energy spectrum peaks at high energies (E$\gtrsim$100 MeV) and extends to very high energies (E$\gtrsim$100 GeV) $\gamma$ rays. In this review we summarize properties of well-studied non-transient $\gamma$-ray binaries as well as briefly discuss poorly known systems and transient systems hosting a microquasar. We discuss also theoretical models that have been used to describe spectral and timing characteristics of considered systems