The background :

In "Reflex: A New Zero-Lag Indicator" in this issue, author John Ehlers introduces a new averaging indicator that he has designed with reducing lag in mind. According to the author, this new indicator can be used to generate signals in a more timely manner than other lagging calculations. This is a continuation of hist article and is the extended TrendFlex indicator (that differs from the "reflex") indicator

It is a sort of a momentum like indicator and should be used like that. Default set is rather long - as usual some experimenting with the parameters should be done prior to using it in trading decisions