What sits in a corner while travelling all around the world?

Why this works

This riddle plays on the clever juxtaposition of the word "corner" and the concept of travel. A stamp physically sits in the corner of an envelope, but it also serves as a ticket for mail that can be sent all around the world. The trick lies in recognizing that while the stamp itself remains stationary in the corner, it facilitates journeys across great distances, making it an amusing and clever answer to the riddle!