What is the lucky money in Hong Kong?

Hello there, I'm curious about a tradition that I've heard of in Hong Kong - the concept of lucky money. Could you please elaborate on what it is and how it's typically exchanged? I've heard it's often given during special occasions like Chinese New Year, but I'd love to hear more about its cultural significance and any customs or rituals that might be associated with it. I'm particularly interested in how it differs, if at all, from similar traditions in other parts of Asia or even the world. Thank you for your time and insight!