According to Engadget conventional phase detection autofocus (PDAF), as featured on most modern smartphone cameras, works by detecting pattern changes in the vertical direction only. In other words, PDAF wouldn't work as well on horizontal pattern changes.
This is where Oppo"All Pixel Omni-directional PDAF" comes in. It detects pattern changes in vertical and horizontal directions to make use of more image data, thus enabling faster focusing and better low-light performance. This allows the sensor to focus on smaller objects or finer details.
Oppo tapped into Sony's "2x2 On-Chip Lens (OCL)" solution, which places four adjacent pixels with the same colour under one on-chip lens, thus turning all imaging pixels into usable pixels for phase detection. A conventional sensor layout would have one lens per pixel, which vastly limited the number of detection pixels.
In addition to its supposedly wonderful camera feature, Oppo confirmed that the Find X2 will be powered by Qualcomm's new Snapdragon 865 chipset, and that it'll deliver a "greatly" improved visual experience -- think higher resolution, higher refresh rate (likely 90Hz or more), greater colour depth and higher dynamic range.