From all that I've read, it indicates that clicking is a sign of a displaced disc, usually forward.
The clicking sound is the jaw snapping back into position underneath the disc. Then, as opening continues, the disc remains in its proper position until full opening. However, shortly before full closure, the condyle slips back off of the disc creating a soft closing pop. Clicking sounds which occur as the jaw is just beginning to open are usually less a problem and easier to treat than those clicks that occur at almost maximum opening. The reason for this is that the disc has not yet slipped very far out of position, therefore, the ligaments holding the disc in position have not been stretched too severely.
Hope this helps.