The Tibetan term for Mandala is "KyilKhor," which means something like "center and circle" or "Center and Circumference."
There are three basic "types" of mandala referred to--the practice of "Offering a Mandala," the "mandala as basis of empowerment" and the "Mandala Practices" themselves.
For the first, there are a variety of more-or-less detailed descriptions of the Mandala Offering-the 37-drop mandala, the 7 drop offering, 23 drops, etc. In all of these practices, though, the idea is to offer specific precious things--substances, geographic features, precious plants, jewels, animals....in short, really, it's an offering of the entire universe. There's much more to say about this, of course, many levels of meaning, which really you need to hear from a teacher when you engage in this practice. Traditionally it's part of the Ngondro, or preliminary practices, though mandala offerings can also be made at the end of a teaching, to one's teacher, or in other circumstances as well.
For the second, the "basis of empowerment" is a diagram of the floor plan of a palace or environment particular to a given practice or deity, as commented on by Heart and by yourself. It can be made of sand or colored powder, or it can be "painted on cloth." Different practices require different mandalas. Even for one given deity, take Chakrasamvara for example, there are a wide variety of practices, and therefore a wide variety of mandalas that would be used. Some of these "Mandala diagrams" are very elaborate, like the well-known "Kalachakra," and some are very "unelaborate," like, for example, Longchen Nyingthik's "Tigle Gyachen." Again, the details of a specific mandala relate to a specific practice, and would only be taught or learned when someone was going to engage in that practice. The book you're referring to is likely a collection of these types of mandalas, along with comments about the symbolism, etc.
The third type, which is the mandala of deities themselves, is the actual practice, the visualization of oneself as deity or deities, and one's environment as palace, etc. These details are codified in the sadhana, which is the text that outlines the visualizations, praises, offering recitations, mantras, etc., for the given practice one is performing. Again, the details vary, and there can be any number of "Deity figures" as well as all types of details of the environment, depending on the given practice. You can understand, therefore, that the mandala diagram referred to as the second type relates to, or is based on, this third type of mandala.
The word "Mandala" is used in other ways, as well....for example, in a given sadhana you may see the words "the syllable Ram transforms into a triangular Fire mandala"etc. But, for the most part, one is talking about one of these three types as outlined above.
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