During this time, the country was split on the idea of tariffs. Not only did tariffs make the North and South feud on the topic, there was also the problem of the balance of power between the federal government and the states.
The idea of tariffs is quite simple, it's taxes that are put on goods that are being bought in foreign countries. If an American wanted to get something from a foreign country there would be a tariff on it, if someone from a foreign country wanted to get something from the United States, there would also be a tariff on it.
The North and South very much disagreed on the topic of tariffs, the North was in favor of them and the South hated them. The North wanted tariffs, as they had mostly industries. This would mean that foreign competition for them would be ruled out and it would be better for American businesses. On the other hand, the South still focused on agriculture. This meant that high tariffs would make their goods less desirable, as they mostly sold them to foreign countries. Since they also bought from foreign countries, that would be more expensive as well.