The good Temple Knight is a symbol of justice, pride and hope, while evil Knights are symbols of tyranny, fear, and death.
The good Temple Knights are an order of Paladins, Cleric/Fighters, and even Cleric/Paladins that use divine power to aid them in combat. The Holy Sword skill they posses is a powerful and devastating tool in their quests. By shaping the divine energy they posses, the Temple Knight calls upon the power of her ideals, or her god, and delivers this energy threw her weapon.
Multiclass notes: A Temple Knight may take further levels in Paladin, as long as they still uphold the Paladins code. But as long as the Temple Knight still upholds the virtue and honor of the order, a Temple Knight does not lose his Paladin or Temple Knight benefits. Evil Temple Knights are more often Cleric/Fighters or even Paladins of Tyranny(see Unearthed Arcana) and the multiclassing benefits still apply as long as they remain evil and devoted to their evil order or god.