As with all fundamental concepts, the fundamental concept of Taoist meditation is very simple. It is the combination of Chi and Consciousness. Through this combination, the body can be strengthened, the mind can be calmed, and immortality of body and spirit can be achieved (of course,immortality is a metaphor and a psyche reality, rather than a physical reality).
For any student of Taoist yoga who prefers demystification rather than mystification, he or she can get this simple concept from reading the classics, for example, Master Wu stated it clearly in his "A direct approach to Immortality" (天仙正理直論, no English translation yet, Mr. Wu (伍沖虛) was the master of Liu Huayang, author of Hui Ming Jing (慧命經): 昔曹老師語我云： 仙道簡易，只神、炁二者而已。 ("my former master told me that Immortality is simple, merely (training one's) consciousness and chi").
Schematically it runs like this:
Let A be chi, and B be consciousness
Training building block = A followed by B followed by A combining with B (A - B - AB).
In actual practice, it is like A1 - B1 - AB1 - B2 - B2 - AB2....to one's limiting physical life.
The core practice mechanics = microcosmic circulation (小周天) + macrocosmic circulation (大周天).
The key training milestones = combining chi and consciousness (i.e. in the zone).