Technical concepts were provided by mbpark in
Understanding HDMI. To appreciate what is described, understand that all communications (even digital) are analog. It's all about the frequency response.
USB solved this problem simply. Any USB cable can be any length as long as its meets frequency response parameters. Only then can it have that USB symbol on the connector. To make a USB cable longer mean the cable nees parameters that make it more expensive.
Same applies to HDMI. However this standard did not create simple consumer standards found in USB. Manufacturers play games by not providing tech specs. It works because so many foolishly rate quality in terms of dollars while completely ignoring spec numbers.
What HDMI cable do you need? Notice Best Buy et al prefers to you stay ignorant. However a simple standard exists to identify scams. If Monster is selling it, then the actual retail price should be somewhere as low as one tenth the Monster price.
Some HDMI cables can have lower frequency response. So a TV, et al displays at lower resolution. Most people don't notice lower resolution 480i signals on their 720 or 1080 TV. So again, they make a sale by keeping the consumer ignorant.