Well my monitor, a samsung sync master, has the port and so does my mobo AND me graphics card? I'm assuming it'd make more sense to hook up the HDMI between the GPU and my monitor instead of the monitor and the mobo...
Also, if either way works, how will I know its working? What will be the difference, if there is one that can be noticeable?
if you have a dedicated gpu, then i would recommend to hookup your monitors to the GPU, because the dedicated gpu, has more performance in the first place, then your igpu or apu, mostly,
if you're gaming the game will be rendered by whatever is driving the display, so if you use the motherboard it will be using horrible by comparison intel/amd graphics, if i wasn't clear enough
if you just use the graphics card for computational tasks however (video editing, crypto mining, etc.) i suppose it doesn't really matter, but around here unless otherwise stated gaming is assumed