Why is this the answer?

The answer is eyes because this is a very old and beautiful riddle that uses word pictures to describe one of the most important parts of your body. It is a puzzle that tricks your mind into thinking about real animals, but the answer is the magical way you see the world. Let us look at the first clue: "Two horses, swiftest traveling, harnessed in a pair." Think about what horses do best: they move quickly! Your eyes are like two fast horses because they can dart all around the room in a tiny moment. If you look at your friend, then the clock, and then the door, your eyes have already traveled and landed on all three objects much faster than any other part of your body can move. They are a "pair" because you have two of them, and they are "harnessed" or connected together on your face. This means they are always working side by side as a team. No matter where you look, both eyes move in exactly the same direction to make sure you have the best view of the world. The second clue is the trickiest and the most fun: "and grazing ever in places. Distant from them." When a real horse "grazes," it is eating grass right in front of its nose. But for your eyes, the word "grazing" means looking at things or checking them out. Your eyes are constantly looking at things, near and far. Even though your eyes are always fixed right on your face, they can look at something very "distant," like an airplane flying high up in the sky or a mountain way off in the distance. The airplane is miles away, but your eyes never leave your head to go visit it. They are still able to see that object clearly from right where they are. They are always staying put on your face, but their sight is traveling to all the far away things they are looking at. That is how your two little horses are the fastest travelers of all, making the whole world visible without ever leaving home.