Chaos magick is a modern field of magical practice, having emerged in the later part of the 20th century, which emphasizes a free-form, nondogmatic approach to magical workings. Chaos magick takes advantage of a few useful quirks in magick; for example, that widely differing approaches and understandings seem to be equally useful in a magical sense, and that what one wants to happen tends to happen. As such, it generally forsakes any concrete system of magical theory, aside from "what works, works."
Chaos magicians are a widely disparate group; due to the very nature of their craft, there are no necessary pattern or tradition of practice between all chaos magicians. However, they are known for using certain techniques and practices which take advantage of what they consider to be magick's true nature. For example, a large part of "typical chaos magick" involves the deliberate assumption of various belief systems, often for some direct magical purpose and almost always temporarily; the reasoning behind this is that belief, and the belief systems which structure it, is a powerful force in magical workings. Therefore, in order to acheive certain ends, a chaos magician may choose to believe (and believe quite profoundly) in some given magical or religious world-view in which his task is easier, or which provides tools for accomplishing it.
Another noted practice for chaos magicians is the use of sigils. Sigils are (usually) linear designs which are associated with, and charged for the purpose of, a specific goal. The exact methods of creating and using sigils vary, obviously, from one magician to the next. Techniques for creating sigils usually focus on granting the design some initial connection to its purpose, techniques for charging them focus on establishing a strong subconscious association between the sigil and its purpose, and techniques for casting them focus on use of gnostic or ecstatic states to throw its power into the world. Through use of sigils, a wide variety of effects can be accomplished; as with the rest of chaos magick, its uses are limited primarily by the skill of the magician, what can be conceived of, and what can be believed in.
A chief criticism of chaos magick is that it doesn't take the profound and important matter of magick seriously, by practicing magick without (consistent) spiritual aspects, and abandoning any attempt at a formal magical theory. Chaos magicians themselves tend to not refute this allegation, countering that magick may not require as much solemnity as many magicians treat it with. This sort of mindset has been the source of a long and fruitful relationship between chaos magick and Discordianism.