Tokyo 2020 explainer: ROC dominates Olympic medal tally but who are these athletes

A total of 335 athletes are taking part as ROC members and they are not allowed to use the country's name, flag and the national anthem.   

If anyone who has been following the Tokyo Olympics closely, he/she must have noticed ROC or Russian Olympic Committee dominating the medal tally. And on close observation one must have wondered, why are the Russian atheletes participating under this banner and not their country name.  So far ROC members have bagged a total of 58 medals, which include 16 gold, 22 silver, and 20 bronze.  So what exactly is ROC?