What is the meaning of "dragon vein"?

Things on the earth's most prominent is the winding thousands of miles of mountains, it moves of ups and downs, and from now on to one of them, as if the earth trembles on pulse.

Fengshui believe that the earth is alive, and it is the pulse of the mountains, angry to walk down the mountain.Longyou by mountains, rolling, revealing as the earth, so the fengshui mountains called the dragon vein.