What that means is that you can either use it to run some extremely low-profile HDMI cables between your AV setup and your TV, or keep it in your camera bag if you happen to have one that can output HDMI video. Personally, I know of a portable Blu-ray player we bring on trips that goes great with such an easily stored, and rather lengthy, HDMI cable.
So what allows for the cable to be so much thinner than the standard HDMI one you will find elsewhere? It's because there is a chip embedded on one of the plugs that is powered by your display device in order to better interpret the data, so that some of the redundancy built into the standard HDMI cables isn't necessary. In other words, the cable itself doesn't have to be as large as the standard products because the RedMere Booster Module will amplify the signal to the desired strength and remove any noise that was generated during the transfer. Because of this extra work, the cables don't have to be as big or thickly shielded.
Basically, where normal HDMI cable setups simply allow the data to flow through them in a passive manner and allow the components at either end to do the grunt work, as they are designed to do, RedMere's active cable design adds a bit more intelligence to the cable and helps to transform the signal back to what the TV is expecting from your other device.
As a result, unlike other HDMI cables, the RedMere varieties have an end labeled for your TV. It very much expects the data to flow in a specific direction if it is going to work.