What is Rolling Correlation?

Question

As above, what is Rolling Correlation? Especially in the area of currency.

Answer 1

When something is said to be rolling it's tracking a certain amount of time in the past, and then rolls forward as time progresses.  So the the 30 day rolling correlation would be the correlation between the basket of assets for the past 30 days.  Tomorrow we add one more day and subtract the first day, to maintain 30 days.