Image source: instaforex.
It is an Oscillator Indicator and enables a trader to decide between divergence and convergence on the price chart. It also indicates the exact point of the market trend change.
If the DPO line crosses the Zero level from bottom to up, it denotes the Buy trend.
If the DPO line crosses the Zero level from up to bottom, it denotes the Sell trend.
Ref: instaforex.