Most different HDMI adapters nowadays are all of very similar quality. Do not fear paying a little less for one, everything will most likely be just fine.
No there is not
Only in build quality. I have a cheap HMDI cable, and one of the terminals came apart. As far as signal quality is concerned, though, there is no difference.
HD stands for High Definition. HDMI stands for High Definition Multimedia Iterface. HDMI is the input for 1080p HD programming. HD is the actual resolution 1920x1080p is the standard for HD...