This spread is based on the Tree Of Life glyph as found in the Kabalah. The cards are layed out in a sequence which follows the "path of the flaming sword", which is the traditional order in which each circle or, "sephira", is manifested on the Tree. The two lower sephira, numbers 9 and 10, are "raised up" to fit between the 7th and 8th sephira to form the pyramid configuration. The first card is refered to as the "key card", while the sixth is called the "core card". The beauty of this layout is in its flexibility. The path of the flaming sword sequence is what generates the spread. The interpretation may then proceed from this literal "Tree of Life" format in which each card is referred to its corresponding sephira on the Tree, and is considered in light of the qualities thereof, or, once the spread has been generated, one may choose to "detach" from the "Tree of Life" format and introduce one or more of any number of possible configurations that form new patterns, or grids, based on various structural relationships. Included are nine samples of possible patterns. Of course, anyone can create their own patterns as well. Often, the placement of the cards will suggest a pattern on there own. This allows for the cards themselves to determine and reveal relationships that indicate story lines, or pictures, that can be used in the interpretation of the spread as a whole. It is very powerful in that it is generated via the connection to the Kabalah:

"...the Tarot, the most satisfactory of all systems of divination, rises from and finds its explanation in the Tree and nowhere else. That may seem a dogmatic statement to the scholarly historian searching for traces of the origin of these mysterious cards, and we may add, most lamentably failing to find it; but when it is realized that the intitiate works the Tarot and the Tree together, that they dovetail into each other at every imaginable angle, it will be seen that such an array of correspondences could be niether arbitrary or fortuitous." -Dion Fortune

So, being based on the Tree, the Pyramid Spread is rooted in a natural setting, and reflects the sacred and powerful energies associated with the ancient system of The Kabalah. This in combination with the variety and flexibility that it offers makes it a very practical layout to use.