Antonín Dvořák wrote Largo as one of the movements, (that’s what the parts of a piece of classical music is called) of his New World Symphony. Dvořák was an immigrant to America and he wrote this piece to show American composers that black people’s music was a really amazing and beautiful part of the American culture. He hoped that more classical composers would use the ideas in black music in their compositions.
There is a radio show that tells the story, but it is probably best if you listen to it with your favorite grownup so they can explain some of the ideas in it. Let them know it’s only 8 minutes long, so it will be quick!