The triangular trade refers to the trade between England, India and China in the eighteenth century.
(i) The English East India Company was buying tea and silk from China for sale in England. As tea became a popular English drink, the tea became more and more important.
(ii) England at this time produced nothing that could be easily sold in China. The western merchants did not have a way to finance the tea trade.
They could buy tea only by paying in silver coins or billion. This meant an outflow of treasure from England.
At last it was decided that opium would be grown in India and transported to China in exchange of tea.