Widdershins means the opposite of the usual.
Deosil is the Gaelic word for clockwise direction. Deosil also means right (not left) and right (not wrong), south (which is on your right when you face the sunrise) and as a general blessing (may things go right).
Walking widdershins refers to walking counter-clockwise or contrary to the Sun’s course and is the traditional path into the Faerie Realm. Widdershins is a Gaelic term with the original meaning “against the way.”
The Sun played a significant role in ancient and primitive cultures. It was relied upon for more than just light, but for survival with crops and harvests to mention a few. Old Gaelic history beliefs indicate that anything that moved against the Sun was negative, evil or unlucky. Many Celtic myths and folklore speak about the Gods and Goddesses forcing people or things to be moved widdershin to bring on turmoil and chaos. The North Yorkshire Moors believed that is you dance nine times widdershins around a fairy ring you will come under the power of the Fae. Moving widdershin is known to bring on havoc and destruction. Modern Witchcraft still uses Deosil and Widdershins
Drawing a circle for ritual is always made in a clockwise or deosil motion. Blessing land, stirring a cauldron, smudging, or consecrating an object is always performed deosil. It is done this way to bring a positive flow of energy. Flowing as you will, as the Wheel of Life for the highest good.
Moving widdershins is about restricting time, destruction and the negative flow of energy and literally grinding us against the Wheel of Life to create mayhem. Chaos magick focuses on the use and implementation of widdershins. Do not be too quick to judge, as it is not always negative. Sometimes you may need to work against the clock, and sometimes you may need to destroy something, albeit without harming others or yourself in the process.
One example would be that widdershins can be used to destroy memories that are restricting us from our full potential. Some practitioners will use this method of magick to attack, hex or bind someone.
It is always best to use the deosil practices, maintaining a positive flow of energy and working with all natural things, not against them.