What can travel around the world while staying in a corner?

Why this works

This riddle plays on the double meaning of "corner." A stamp can be affixed to the corner of an envelope, allowing it to travel around the world as the envelope is mailed. The clever twist is that while the stamp itself stays in that corner of the envelope, it can still be part of a journey that spans the globe, highlighting the juxtaposition of its stationary position and its far-reaching potential.