Mandala in Sanskrit means circle or "sacred circle". In Tibetan Buddhism, Mandalas are believed to be the physical embodiment of Buddha. In various spiritual traditions, mandalas may be employed for focusing attention, as a spiritual guidance tool, for establishing a sacred space, and as an aid to meditation and trance induction.
In common use, mandala has become a generic term for any diagram, chart or geometric pattern that represents the cosmos metaphysically or symbolically; a microcosm of the universe.
My point of view of any image that starts from a central point going outwards in a symmetrical fashion, is like a snapshot of the cosmos, as in: your life is "unrolling" in time, and you take a
picture with your eyes (instead of a camera) and "freeze" that image onto a surface. A depiction of that vortex, or forward tunnel of life.
When you purchase a Mandala, go for the one that "speaks" to you. If you pick a particular one, it is likely because it touched a chord deep inside. When you hang it, just use a plain nail (even one of those stick-on hooks works) and hang the Mandala in a way that you, at that time, consider "this is right side up". Whenever you feel it should be rotated, don't question your intuition, just hang it the way you feel it should be. Clockwise means that the energy will be "pushing further", counter-clockwise will restrain or "hold back" the energy, much in the way tarot cards would (upright or reversed). By the way - the square Mandalas can be hung 8 different ways, including the corners.
Hang it somewhere you will be able to contemplate on it comfortably every day, as in: at the breakfast table, on the wall opposite your bed, in your office. Be adventurous, think outside the box: maybe in the nursery on the ceiling, a hospital, the bathroom, travelling, in the room of a dying person. Don't be afraid to touch your Mandala. A protective varnish allows for handling and gentle wiping.