In the Mexico Olympics, John Carlos received the winner medal without wearing shoes. What does this signify?

To represent poverty among the black.

In 1968, Mexico Olympics, John Carlos along with Tommie Smith received their winner medals wearing only black socks and no shoes. This was to express the poverty among the black and draw international attention to the racial discrimination faced by them. They raised their black-gloved fist during the playing of national anthem. Many people around the globe were outraged and expressed support towards this action.