According to the Wiccan tradition there are Five Elements, which are the forces that every life form is build from. When a Witch invites the Elements, she invites the symbolic and yet real forces, that each and every thing in this Universe contains.

Most Witches welcome the Elements right after the circle's been cast, my version to do this is in the 'Casting a Circle' part.
The Elements are:

Earth- Mother earth, stability, slow, pounding like the beat of the heart, earth ancient wisdom, represents all the physical expects of life.
The traditional direction of this Element is the North, the place of the great Darkness.

Air- Imagination, creativity, learning, flying, the element of the mind and intelligent thought.
The traditional direction of this Element is East, the place of the beginning.

Fire- Protection, battle, heat, leadership, success, the element of burn and change.
The traditional direction of this Element is South, the place of the most sun and heat.

Water- Flowing, shifting and shafting, love, caring, affection, listening to yourself, instincts, sub- continence, the element of emotions.
The traditional direction of this Element is West, the place of sunset and reflection.