I'm trying to understand light sheets as related to the holographic entropy bound for information. This bound equates the information on a surface (e.g. the event horizon of a black hole) with the information that can be stored in a volume (holographic principle).
I have looked at a lot of diagrams but I still don't quite understand geometrically what a light sheet actually is and how they are defined. (Presumably it defines a space-time volume?)
As far as I understand the entropy bound states that the entropy of matter on a light sheet is never larger than the area of an attached spherical surface or screen (but this is also sometimes a screen at infinity). However I don't really fully understand the geometry of the light sheet or how it relates to the surface or 'screen'.
Can someone please provide a clear definition of a light sheet, and its relation to the holographic surface?
In addition, what's the intuition that the information on the light sheet is related to the surface in question?