One at the other, but the difference here is that it isn't switched. In fact, having bought a couple of these from CPC a few months earlier, I ordered some more for this new setup, but by then the listing had changed to introduce a red warning that this cable isn't a splitter!
I don't know exactly what it is then! It's possibly in fact a "joiner" or "combiner". I had been using one of these leads to split the RGBtoHDMI output from Station 201 so that one of the outputs would go the monitor and the other to my PC via the USB to HDMI capture stick I use for screengrabs.
The the problem I always had with it was that both receiving devices shall we call them, ie. the monitor at Station 201 and the PC with capture software running (OBS Studio in my case) have to be running to get a picture. If only one is on, there's no picture. This was a bit of a nuisance of course as I didn't always want my PC turned on and USB stick connected and OBS Studio running just to use Station 201!