Slavery is when about 12million African slaves were moved forcibly from Africa to the Americas by a Middle Passage. About 15% died on the journey.
African men were forced to stay below deck and they were all compacted together so there was barley enough room to even walk around. A lot of Slaves got sick because it was so dirty under deck and they would get diseases. Women and children stayed on deck and were beat.
Things are being traded from other countries. For example, America is giving Europe "raw materials", like cotton and wood. Then in exchange Europe would send back clothing or furniture. Their economies are trading goods throughout different countries.
Africa would send gold and iron to Europe. And for the Americas, they would exchange for work. America needed a lot of work, and for that Africa gave America Slave Labor.
Mercantilism is about the competition between different kingdoms. They wanted to gather as much gold and silver as they could get. Their colonies believed that the world was all about wealth. So with gold and silver they were competing for that wealth.
KIngs wanted export as much as possible while importing as little as possible so it would be balanced with other coutries.