It is good of you to be curious about what concept art is. There is a lot of misleading material out there as in lots of really cool illustration but not much clear understanding of what concept art actually is. Not to say anything out there is wrong, just not as direct as it could be. This image was part of the early stages of development and is more of the "blue sky" stage where anything goes. I was trying to sell this idea by making it look grand and menacing, but we went a different direction. This eventually became a complete underground laboratory BELOW a different level. I would say the best place to start is draw, draw a lot, and then draw more. Painting is important, but drawing is faster and can convey design easier. (then you can paint over it and make it look pretty).