I've been reading some pretty interesting material on the subject of Dzogchen buddhist practice recently.
Essentially, Dzogchen is a form of practice in which the subject for meditation isn't your breathing, or a mantra, or a candle, or anything at all like that. Instead, Dzogchen practice involves studying the nature of mind itself as the object of meditation. The concept suggests that careful, naked examination of the nature of mind-itself, all by itself, can lead to enlightenment. Here is where you come into phrases like "clear luminosity" to describe the essence of mind.
This is pretty heavy, estoteric stuff, with subtle nuances that go on, and on, and on. Dzogchen appears to be very, very old, dating back to the shamanistic days of the original Bon religion of Tibet. It was then adopted and modified by Buddhism when it migrated into Tibet from India.
The essence of the practice is that looking at the mind in a very detached, objective way allows you to see that thoughts and feelings all arise and are self liberated within the arena of mind-itself, with no real help from us, and not much burden. While all that arises in the mind is utterly temporary and without substance, the mind itself is timeless, in that it isn't born and doesn't die.
The practice is really about allowing yourself to relax into mind-itself, and simply allow thoughts and feelings to come and go as simple expressions of the mind, but without any more significance than that. As a common analogy goes, it's keeping the sky in mind, but not being distracted by the clouds.
In the context of this recent study, I came across an idea that struck me as very interesting. The commentator was observing that what we take as "reality" virtually always contains a large percentage of mental elaboration and modification. What we take to be "real" is actually merely an idea of what is real.
Life become much simpler and much pleasanter, if we keep in mind that that what we experience is almost always a large part mental ornamentation and imagination, and hence should be treated playfully.