What is the Re-grid method?

I was wondering what is the re-grid method in the processing parameters of the Radiometric Terrain Flattening. I can do this terrain flattening for my data just by unchecking this re-grid method box in SNAP. Just wanted to know how it might effect my final results?

The re-grid method is better because it computes the simulated image on the DEM grid. If re-grid method is unchecked, it computes the simulated image in the SAR frame.