It checks our real time forex data every minute and determines the current strength. You might want to stay away from trading those pairs. Conversely, if two currencies are weak, strong or average strength, there is often a range or sideways movement happening.
Such deviation between pairs usually indicates momentum. For instance, if a certain currency is very strong, and another suddenly turns weaker, you may find a trading opportunity. It is useful as a quick guide to which currencies you might want to trade, and which might be worth staying away from. It then bundles together each the associated pairs to an individual currency (eg, EUR/USD, GBP/USD, USD/JPY, EUR/GBP, AUD/USD etc) and finds the current strength.
The currency strength meter takes readings from every forex pair over the last 24 hours, and applies calculations to each. How Does The Currency Strength Meter Work?