HP 839512-001 is the SPS-PROC G3900 processor, a desktop CPU for a compatible system. The part number identifies this specific HP processor assembly.
Its Intel Celeron G3900 runs at 2.8 GHz and has 2 MB cache, with 2 cores and 2 threads for everyday computing tasks. The processor uses an LGA 1151 socket, so its fit is defined by that motherboard interface.
Intel HD Graphics 510 is integrated into the processor, providing graphics capability without a separate graphics processor.