While the game rages, the one in the lead is marked by a floating crown over his Icon. This crown floats form one Icon to another when someone else takes the lead.
When the match is over, players are taken to a score screen. This screen shows who won, who lost and who really, really lost. If you play logged in with your account, then the game adjusts your personal score based on the results. This ensures that in the future, you will be matched up against opponents on your own level. If none are available, and you are paired up or down, then this will be reflected in how the rounds’ score affects your personal score.