Admit it: You’re not 100% sure what duty-free is. Well, it's time to find out! Here’s what you should buy duty-free at the airport, along with the rules to abide by.

Maya Kachroo-Levine is the digital senior editor at Travel + Leisure. She covers hotels, destinations (focusing on Europe, Asia, California, and Mexico), food and drink, cruises, and luxury aviation.

Dubai: TerraPay, a global money movement company, has joined forces with Dubai Duty Free (DDF), the world’s largest single ...