Every person who is initiated into Wicca is a Priest or Priestess. This is based on the idea that, by choosing Wicca as our path of spirituality, we are taking spiritual authority over our own lives.
As opposed to other religious traditions, Wiccans do not require a member of the clergy to perform sacred duties and rites of passage for them. Each Wiccan is considered to be a priest or priestess, fully capable of discerning the Divine will in their own lives, and to act for their own spiritual benefit.
A Wiccan Minister takes on the additional responsibility to be of spiritual service to others. This generally includes roles that are usually associated with clergy of other religions, including listening and counseling a person in emotional distress, offering guidance and advice on spiritual matters, or performing rites of passages such as handfastings (marriages), Wiccanings (Baptisms), and funerals. They generally work (whenever possible) within the person's own spiritual context, and don't ever proselytize.
Other Wiccans may perform these very same services, but they are under no spiritual obligation to do so. A Minister often is, because they frequently swear vows of service directly to the God and Goddess. They are often “called” to the Ministry. It’s not a role chosen lightly because of the self-sacrifice of time and energy involved.
~Flame RavenHawk