HDMI cables are mainly used to get the best quality of video and picture and also the quality of the sound is better. When they were introduced first in the market it was really expensive but with its growing popularity the price came down. These cables are mostly used in the televisions sets and also in the home theatre systems. If you have a Blu ray player then also you would be able to use this cable.
Since the cost of the HDMI cables have come down it does not mean that you would purchase the cheapest of them all because the quality of the cables also matters. It is always better to choose the cables that have an average price and you must always buy those that are branded. So if you are still using the component cables then it is time that you upgrade as soon as possible.