Often, knights in fiction are seen as noble figures. They have a certain grace about them, not just in combat but also in their interactions. They are polite and courteous, which is part of their chivalrous nature. They are also usually on a journey or a mission. This could be to rescue a damsel in distress, to find a holy relic, or to defend their land from invaders. Their loyalty is not only to a person or a place but also to an ideal, like the concept of good against evil. Their horses are also an important part of their image, being strong and well - trained companions in their adventures.
One common characteristic is their courage. They face danger without hesitation. Another is their sense of honor. They keep their word. And they usually have some sort of loyalty, like to their kingdom or a noble cause.