Partitions a geometry using uniform divisions per axis where each partition will have a unique integer value.
This is an easy way to multi-thread groups of points to be processed in parallel. For example if you want to compute the average point position of all these points, you could process each partition inside a For Loop network and run the same VEX code there to get faster performance.
Of course in this case I would recommend using Attribute Promote, but this is just one example.
https://www.dropbox.com/s/5paepsyblhwh6vw/GridPartition_SOP_Animatrix.otl?dl=1