Explain the medal ceremony of the 200 meter race in Mexico city?

The medal ceremony of the 200 metres race in the 1968 Olympics held at Mexico City. The two men standing with clenched fists upraised and heads bowed, while the American national anthem was played, are the US athletes, Tommie Smith and John Carlos. They are AFRICAN-AMERICANS. They had won the gold and bronze medals respectively. They received their medals wearing black socks and no shoes to represent Black poverty. With this gesture, they racial discrimination in the United States. The black-gloved and raised clenched fists were meant to symbolise BLACK POWER. The silver medallist, white Australian athlete, Peter Norman, wore a human rights badge on his shirt during the ceremony to show his support to the two Americans.