An aide-de-camp is a military officer acting as a secretary and confidential assistant to a superior officer of general or flag rank.
In modern times aides-de-camp are usually of junior rank and their duties largely social. Military, naval, and air force officers, frequently of high rank, who act as aides to chiefs of state, such as kings or presidents, are also called aides-de-camp. In many countries, the word adjutant is used for aide-de-camp and adjutant general for a royal aide-de-camp.
On Napoleon’s staff such officers were frequently of high military qualifications and acted both as his “eyes” and as interpreters of his mind to subordinate commanders, even on occasion exercising delegated authority.