Look up in the sky! It's a bird…it's a plane…it's SUPER KNIGHT! Seriously, this guy is one perfect knight. If there's been a battle in the past twenty years, chances are good he was there. In all of Christendom and Heathendom, there's no man who's ridden farther. Alexandria, Belgazir, Prussia, Lieges – you name the battle, he's fought in it. And not only that, he's probably been the hero of the battle and won a prize or two, or a place of honor at the victory banquet, as well. He's sort of like a football hero; you know the type – the guy who makes every touchdown and gets carried off the field on the shoulders of his teammates.
But not only is the Knight a stellar battlefield athlete, he's also a genuinely nice guy. Chaucer tells us that he's never, in all his life, spoken a harsh word to anyone. On the pilgrimage, he's the peacemaker of the group, calling for reconciliation between the Host and the Pardoner when the Host takes offense at the Pardoner's attempt to sell fake relics to the pilgrims.
Unlike with some of the other characters, we can be sure that this knight is exactly what Chaucer says he is. How do we know? Well, because although he's got a really beautiful horse, he's wearing a tunic that is still stained with the blood of his last battle. He's literally walked straight off the battlefield and into The Canterbury Tales. Also, the story the Knight tells is exactly what we'd expect of a perfect knight: it's a tale of two friends who pine away for the same noble woman, replete with jousts, battles, and courtly love. And finally, the Knight's son, the Squire, reflects well upon the Knight because he, too, is a perfect gentleman. That kid was raised right. It would be hard to be otherwise when your dad's such a perfect knight.
In The Canterbury Tales, the Knight is a representative of those who belong to the very high social class of the nobility. His behavior – peacemaking, speaking like a gentleman, telling a polite romance – is probably meant to provide a point of contrast with the very different "low-born" behavior of characters like the Miller and the Reeve.