The Qabalistic "World of the Shells," the backside of the Tree of Life, also said to be reflected beneath it. Trying to render three-dimensional esoteric geometry on flat scrolls is such a pain in the ass, isn't it? According to Qabalistic doctrine, the Qlippoth were created when the intensity of the divine essence shattered the first creation. All that remains are its pieces. The Qlippoth are also described as excrement, or as accretions around the ten bright sephiroth. Funny how the oldest thing is considered the waste of the new. There is probably an arcanum there, or a load of shit. (Remember, contradiction is unity but only above the Abyssof Knowledge (Da'ath). The Qlippoth are generally viewed as dark and primal, sometimes said to form a Tree of Death (Or maybe the Tree of Knowledge!). Odd then, that their attributes are represented as perversions and corruptions of the standard ten. The Qlippoth are said to be connected by "tunnels" rather than "paths" as is the case on the light side. Also, the Qlippoth themselves are sometimes called "cells." They are not organized in any rational way, nor, it is said, can they be scried into. Rather, one must explore them firsthand. Amusingly (or perhaps disturbingly) they are apparently accessed by diving into the Abyss, like going through a black hole to another universe.
A final note some regular users will undoubtedly find amusing: The Angel of the Qlippa of Yesod, the Moon, is called Gamaliel, entitled "The Obscene Ass."

In Kabbalah, klippoth are sephiroth which are considered to be empty and/or broken. Considered to be a bad thing as they tend to drain your energy or at the very least block your flow of power.

Following discofever's "trickle-down" analogy in sephiroth, think of klippoth as being similar to clogged or leaky pipes, producing a really nasty mess.

It's rather like this node which may
have served a purpose by filling in
some info missing from the sephiroth
node, but is slowly draining my XP.