Can you explain the concept of demilitarized zone?

The concept of the DMZ, like many other network security concepts, was borrowed from military terminology. Geopolitically, a demilitarized zone (DMZ) is an area that runs between two territories that are hostile to one another or two opposing forces' battle lines.

The DMZ likewise provides a buffer zone that separates an internal network from the often hostile territory of the Internet. Sometimes it's called a "screened subnet" or a "perimeter network," but the purpose remains the same.