Many of us are bought up within a monotheistic religion. We are taught that there is one God and that we should have no other God (let alone a Goddess). The Goddess was held in great esteem by many ancient peoples throughout the world. Alongside her were the Gods, in many forms and with many names, depending on where in the world you lived. Statues and ornaments have been found dating back thousands of years, all showing the existence of religions honouring the male and female.
The concept of Goddesses and Gods in Wicca can be difficult to understand. Some people are very much attracted to a certain deity, in which case, with further reading and investigation about them, you may have found one you wish to work with on a regular basis. Others find that meditation and visualisation, help focus the mind on a particular Goddess/Go.
The Jungian concept states that every soul is composed of Anima (Female Polarity) and Animus (Male Polarity) and should be equally explored by both sexes.
Whereas the Goddess is omnipresent, the God is more dynamic in that he comes and goes and sparks change and movement in the state of things.
Some witches will be wary of invoking Pan at a ritual. His name means 'all' in Greek. He was half man, half goat, but his name also relates to pandemonium, so be careful!
The Great God/Lord unifies everything as he is the Son/Consort/Lover of the Goddess. Witches mostly relate to him as the Horned God, ruler of the forests and animals. He is the link between all living things as they manifest in the physical world and the tie that binds the Goddess/Lady's creations. He provides by hunting and balances the life/death interactions of all life forms.
He is know by many names:
Lugh: Celtic: Sun God and God of the arts. His festival is Lammas.
Apollo: Greek: son of Zeus, the God of sun and light, truth and prophecy.
Dionysis: Roman: The God of wine.
Odin: Germanic: Also known as Woden or Wotan: He was the chief God of Germanic mythology.
Shiva: Asian: Shiva is one of the principle Hindu deities, who together with Vishnu and Brahma, forms the Trimurti, or triad of great Gods.
and many others.