 According to the standard definition (Hawking and Ellis 1973; Wald 1984), the event horizon of a black hole is the surface formed by the points of no return. That is, it is the boundary of the collection of all events in the spacetime closest to the singularity at which a light signal can still escape to the external universe. Everything including and inside the event horizon is the black hole itself. (See  section 3.4  for a discussion of different ways to define a black hole, and the problems these competing definitions raise.) For a standard (uncharged, non-rotating) black hole, the event horizon lies at the Schwarzschild radius. A flash of light that originates at an event inside the black hole will not be able to escape, but will instead end up in the central singularity of the black hole. A light flash originating at an event outside of the event horizon will escape (unless it is initially pointed towards the black hole), but it will be red-shifted strongly to the extent that it started near the horizon. An outgoing beam of light that originates at an event on the event horizon itself, by definition, remains on the event horizon until the temporal end of the universe. 