Yes; it's a lead to connect a remote trigger to some Nikon bodies. Tends to be generic releases which have a standard sender/receiver into which that lead (or one suitable for the system in use) plugs.
Use the Nikon one, something like 15 quid, wireless remote. PerfectCool, I'm actually needing a remote shutter trigger for my D750, maybe somebody might have a spare trigger that I can use this with![]()
Will throw it in with the 200-500 lol!
. Will let you know if I come into some serious cash, but could be a long while