As a general term, triangular trade is a system involving goods from three locations, each of which has a demand in one of the others. Goods from location 1 are transported to location 2, where they are traded for local goods; the goods from location 2 are transported to location 3, where they are traded for local goods; then the goods from location 3 are transported to location 1, where they are traded for local goods. The trade goes on and on, to the benefit of the traders, the shippers, and, hopefully, the people in the locations involved.
As a specific term, the Triangular Trade was a system in which African slaves were traded for agricultural produce, which was traded for New World manufactured goods, which was traded for European manufactured goods, which was traded for slaves.
Typically, the slaves were taken by ship from Africa to the Caribbean, where they were traded for molasses. This was taken to New England and traded for rum and ironware. These were taken to Britain and traded for weapons, beads, copper, cloth, and whatever else traders though might appeal to people who sold slaves in Africa. And these were traded for more slaves.
A trade thourgh North America, Afirca and Europe. If you draw it on a map it makes a triangle. This trade was made when Columbus found North America. They got slaves from Africa, livestock and corn from Europe, and North America had new fruits and veggis, the cocoa bean, and other unknown crops at the time.