Overview
White flags have had different meanings throughout history and depending on the locale.
Contemporary use
The white flag is an internationally recognized protective sign of truce or ceasefire, and for negotiation. It is also used to symbolize surrender, since it is often the weaker party that requests negotiation. It is also flown on ships serving as cartels. A white flag signifies to all that an approaching negotiator is unarmed, with an intent to surrender or a desire to communicate. Persons carrying or waving a white flag are not to be fired upon, nor are they allowed to open fire. The use of the flag to request parley is included in the Hague Conventions of 1899 and 1907:
The improper use of the flag is forbidden by the rules of war and constitutes a war crime of perfidy. There have been numerous reported cases of such behavior in conflicts, such as combatants using white flags as a ruse to approach and attack enemy combatants, or killings of combatants attempting to surrender by carrying white flags.
From Wikipedia (CC BY-SA 4.0).