Assuming you mean the Volkswagen/MFD RNS 510 head unit with firmware 5238, here are its likely features and changes in that firmware build (reasonable defaults based on common RNS 510 firmware updates):
Many versions of this firmware include a hack that allows DVD playback while driving faster than 5 mph. rns 510 firmware 5238
It is crucial to match firmware to the hardware version of your unit to avoid "bricking" the device. The RNS 510 has several hardware versions (typically labeled on the sticker on the top of the unit): Assuming you mean the Volkswagen/MFD RNS 510 head
If you are trying to turn your RNS 510 into an iPad, no firmware will help you. But if you want the for your MK6-era VW, Firmware 5238 is the "set it and forget it" gold standard. But if you want the for your MK6-era