These two directions are not the same product and they are not interchangeable. A DisplayPort output can be talked into emitting an HDMI-style signal on its own, through the optional dual-mode feature written into the DisplayPort standard, which is why a cheap passive dongle works that way round. No equivalent exists for a DisplayPort input receiving HDMI. Sending HDMI into a DisplayPort screen requires a converter with a chip inside that rebuilds the signal.

So if the picture is coming out of a laptop, a console, a mini PC, a set-top box or a capture device with only an HDMI socket, and the screen in front of you only has a free DisplayPort socket, this is the page you want. If it is the other way around, you need a DisplayPort-to-HDMI adapter instead, and turning one around will not work in either case.