Photoelectric effect is the phenomenon in which

 photons come out of a metal when it is hit by a beam of electrons

photons come out of the nucleus of an atom under the action of an electric fold.

electrons come out of metal with a constant velocity which depends on the frequency and intensity of incident radiation.

electrons come out of metal with different velocities not greater than a certain value which depends only on the frequency of the incident light and not on its intensity.