A core principle of International Humanitarian Law is the principle of distinction. Armed forces and combatants are to distinguish between combatants and non-combatants.
A combatant (also referred to as soldier or fighter) is a member of an armed group that is part of an armed conflict, except for religious or medical staff, that takes part in the hostilities.
A non-combatant is either a civilian or a combatant that no longer takes part in the armed conflict (also referred to as "hors de combat") and therefore is no longer considered to be a legitimate military target.