The Geneva Conventions are a series of treaties within international law that dictate how persons involved in war--soldiers, civilians, and prisoners-of-war (formerly called "POWs" now called "EPWs" (enemy prisoners of war)--are to be humanely treated, and which actions by warring countries or parties are sufficiently excessive such that they become war crimes, genocide, and/or crimes against humanity.
History of the Geneva Conventions:
see this article in wikipedia for a good introduction:
The International Committee of the Red Cross (ICRC) was first charged with overseeing humane treatments of civilians and combatants in war. However, as the "cross" of the Red Cross is a Chrisitan symbol its sister organization is called the International Committee of the Red Crescent (the "crescent moon" being an acceptable Muslim symbol), and operates in Muslim areas of the world where a "cross" is problematic.
The ICRC works around the globe to ease the suffering of war victims and soldiers alike: