Why is this the answer?

The answer is stamp because this clever riddle uses a fun trick with words to describe a very ordinary object that actually does a lot of traveling. Let us look closely at the second part of the riddle first: "stays in a corner." Think about a letter you might send to a friend or a family member. When you put a stamp on the envelope, you always stick it right in the top corner of the paper. That stamp is fixed there forever on that one spot of the paper. It does not move to the middle or the bottom; it stays perfectly still in its corner. Even when the letter is opened, the stamp remains attached to the envelope. This is why the clue, "stays in a corner," is a wonderful clue that points right to a stamp. Now, let us think about the first part of the riddle: "goes around the world." Even though the stamp itself is stuck in that little corner, the entire letter is about to go on a grand journey. Once you drop the letter into the mailbox, the post office takes over. That letter gets to ride on speedy airplanes, big delivery trucks, and long trains, traveling across cities, states, and even oceans to reach its final destination, which might be very far away. Since the stamp is glued right there in the corner of the envelope, it gets to go on the entire amazing trip, too. It is a tiny, faithful traveler that rides along on the whole big adventure around the world. The riddle is tricky because it makes you think of something huge, like a ship or an airplane, for the "goes around the world" part. But the true answer is the small piece of paper that makes the trip possible. A stamp is the perfect match because it is stuck in one corner, but it helps an important message travel all the way across the globe.