Many astrophysical objects -- such as stars, stellar and galactic disks -- appear to lose mass through supersonic outflows. The model for these supersonic outflows in which radiation pressure is the driving force gains support from observations and detailed numerical calculations. In this talk, I summarize the essential concepts underpinning the model of radiation-driven winds from variety of astrophysical environments. One of the critical aspects of radiation driving is how the radiation momentum can be transfered to the matter. As the temperature of the matter increases, radiation pressure can be predominately mediated by dust opacity, bound-free opacity, bound-bound opacity and electron opacity. Thus dealing with radiation-driven winds we face two basic astrophysical problems: the problem of radiation transfer and the problem of photoionization. To illustrate how the radiation force can explain launching and acceleration of winds, I present two-dimensional, hydrodynamic calculations of radiation-driven winds from luminous stars and accretion disks in which the radiation force is mediated by bound-bound transitions. I summarize the main results for disk winds and compare them with spherical stellar winds. Finally, I discuss applications of the radiation-driven disk wind model to cataclysmic variables and active galactic nuclei.