Original: During war (especially World War I), it is a term used for the area of land between two enemy trenches that neither side wishes to openly move on or take control of due to fear of being attacked by the enemy in the process.
Simplified: During war (especially World War I), it is a term used for the area of land between two enemy trenches. Neither side wanted to openly move on or take control of because they feared being attacked by the enemy in the process.