Positive distinctiveness is a component of Social Identity Theory and is when a social group is made to appear more positive and valued by using verbal and non-verbal cues. Individuals seek to build and maintain positive distinctiveness for their group. Positive esteem is essential for a group and it is usually attained by a comparison to an outgroup on some dimension ('we are better than they are'). Increased ingroup/outgroup thinking (us vs. them) makes the groups more stratified and increases the positive perception of the group.
A common example can be seen with sports teams. Fans often compare themselves to rivals and use positive distinctiveness to elevate the esteem of their team.
More information on ingroup.