Tariffs is a tax on imported goods. When a ship full of bananas or T-shirts or Toyotas arrives at a U.S. port, part of the paperwork for crossing the border is paying the applicable tariff, also known as an import duty. The importance of tariffs is because they can protect domestic industries, raise government revenue, and be used as a tool for trade negotiations or to address perceived unfair trade practices, but they can also lead to higher prices for consumers and potentially harm global trade.
They should be important to citizens because they can impact consumer prices, influence domestic industries, and affect international trade relations, potentially leading to higher costs, job losses, or retaliatory measures from other countries.