In 1998 the UNESCO has proclaimed August, 23 in 2017 as the International Day for the Remembrance of Slave Trade and of its Abolition. Slave trade means to sell and buy slaves and often refers to the enslavement of black African people who were traded to North America and the Caribbean. Basis of all that was the Hamites theory about white people being superior to black people.
After Great Britain had banned slavery in 1807 they also started to fight slavery in other European countries. Little by little slavery then had been banned by all European countries and the transatlantic slave trade dried out. The children's slave trade in Western Africa is one sad example for slave trade still being an issue nowadays.