Canon 5D Mark IV's sensor has a somewhat unusual pixel arrangement: each pixel is composed of two subpixels. If Dual Pixel RAW mode is enabled in the camera, the resulting CR2 file contains two images, or two frames: one composite, made from reading both subpixels, summed; and the other is made out of one set of subpixels.
In essence, in Dual Pixel Raw mode, the camera records into one file some equivalent of two shots, bracketed by (approximately) 1 EV.
The DPRSplit application is intended to extract this additional frame out of the CR2 taken in Dual Pixel RAW mode, and save it as a DNG. Resulting DNG files can then be opened and processed in (practically) any raw converter featuring DNG support.