Wicca (or Witchcraft) is a nature based religion.  I use the words wicca and witchcraft interchangeably, but some don't.  I am an eclectic witch, which means I don't follow a set tradition, but I do use some things from the Corellian Trad.  I believe in the God and Godess and the deities, but I think the Goddess affects females more and the God affects the males more.  I usually pray to the Goddess.  You can refer to the God and Goddess as afore mentioned, or Lord and Lady, or subsitute them with specific dieties.  The dieties you chose are the ones that suit you or your tradition if you have one.  You can choose from Celtic, Egyptian, Greek, Roman, etc.  Mine are Artemis and Bast.  The reason I love Wicca is that you can choose what suits you.