Every army has a heroic character to command it. We refer to this character as the General, although this is only to distinguish him from other heroes. He might be an Orc chieftain, a Bretonnian duke, an Elector Count of the Empire, etc. Many armies are commanded by the ruler of their entire nation. For example, the Emperor of the Empire and King of Bretonnia are mighty warriors who are ever ready to ride out at the head of their forces.
The General of your army is always the character with the highest Leadership value. If several characters have the same value then choose one to be the General at the start of the battle. He is in command of the whole army and represents you personally. The General is an important character because he can inspire others to fight on where otherwise they might turn and flee.