What is Buffer Zone?

Legal Definition
A buffer zone is generally a zonal area that lies between two or more other areas (often, but not necessarily, countries), but depending on the type of buffer zone, the reason for it may be to segregate regions or to conjoin them. Common types of buffer zones are demilitarized zones, border zones and certain restrictive easement zones and green belts. Such zones may be, but not necessarily be, comprised by a sovereign state, forming a buffer state.

Buffer zones have various purposes, political or otherwise. They can be set up to prevent violence, protect the environment, protect residential and commercial zones from industrial accidents or natural disasters, keep prisoners intent on escaping from rapidly acquiring hostages or a hiding place, and have uses in several other scenarios. Buffer zones often result in large uninhabited regions which are themselves noteworthy in many increasingly developed or crowded parts of the world.
-- Wikipedia
Legal Definition
A neutral area serving to separate hostile forces or nations.