Banishing is a magickal operation by which a space or thing is purified and cleaned of all residual "energies" or "magickal entities". It is analagous to wiping a blackboard clean before starting to write. It has a profound effect on the consciousness of the participants clearing their minds of mudane concerns and allowing them to concentrate fully on that which follows.
Although often overlooked by many practitioners in their hurry to get on with the "meat" of a ritual, it is a very important part of many magickal operations. It is usually found that a good banishing prior to a ritual increases the perceived success overall.
There are few purely banishing rituals. Even the most simple (but beautifully elegant) of Magickal operations, the Lesser Banishing Ritual of the Pentagram (LBRP), contains both banishing as well as invoking portions. Incidentally, the LBRP is thought of by some people as a "basic" or "beginners" ritual since it is often the first ritual that people learn. This is quite a flawed view however because despite being relatively simple and easy to learn, the ritual contains many levels of complexity and its purpose; drawing the energy of God, Deity, the universe, in the form of golden-white light into the practitioner; is perhaps one of the greatest magickal acts that may be attempted. Many other rituals that are apparently more complicated draw their structure from that of the LBRP.
Other forms of banishing may be less obviously structured. They may include shouting, banging drums, clapping, humming or silent meditation. As long as their purpose of clearing a space in the physical and mental realities of the practitioners is fulfilled, the method may vary as the participants will.