The world is watching anxiously as the United States moves to introduce tariffs on key trading partners. But what exactly is a tariff? What are the pros and cons, and is there an end goal that Trump has in mind? And to what extent could it shock the world's economy? We're joined on this week's episode by Sharyn O'Halloran, the SALI professor of Political Economy in the Economics and Political Science Department at Trinity College Dublin to put tariffs under the microscope.