After reading this article, You will have a clear understanding the different expertise of these 3 groups of Taoists and their relation with one another.
Expertise of Tang-Ki （童乩）
Folks that are possessed by Taoist Deities are known as Tang-Ki （童乩） in Hokkien and Teochew Dialect , meaning Taoist Spirit Mediums. Taoist Tang-Ki Worship is a ritual to invite Deities to possess the spirit mediums.
Taoist Spirit Mediums and their helpers are only trained in the proper procedure to let the Deities possess their bodies. Helpers in Taoist Tang-Ki Worship, are only trained in creating Talismans needed for Tang-Ki Ritual and the incantations needed for 3 purposes: 1) Inviting Deities to possess the mediums, 2) Send off the Deities and 3) Wake the Taoist Spirit Medium up after the trance.
When they are in trance, Deities would give consultation, draw and consecrate the talismans for the devotees. Most of the Taoist Mediums and Helpers know nothing more than the standard talismans and the incantations needed for Taoist Tang-Ki Worship.
Related Article: Taoist Spirit Medium
Video On Tang-Ki Worship
Expertise of Taoist Priests
Taoist Priests focus their time on major events like reciting Taoist Scriptures in the Taoist temples during important Taoist Festivals. Taoist Priests make their appearance in a big crowd of devotees, wearing Beautiful Taoist Robes.
Taoist Priests do have the knowledge of creating Taoist Talismans to handle human issues but folks seldom consult them for personal problems, or seek their help for spell-casting purposes. Their main task is focused on reciting Taoist Scriptures during Taoist Festivals. They hold very high ranking during Taoist Ceremonies.
During Taoist Tang-Ki Worship in the Temple, when the Taoist Spirit Mediums are already possessed by Taoist Deities, Taoist Priests are still engaged to do the major important ritual (Example: Paying respect to the Great Jade Emporer) and the Deities (Possessed Taoist Spirit Mediums) will lead the Devotees to follow the command given by the Taoist Priests during prayers.
Expertise of Taoist Magic Masters / Sorcerers
Taoist Magic Practitioners fall into 2 categories:
1) The Taoist Masters
Taoist Masters only follow the "Right" Path and Do No Evil. The spells they cast and rituals they do are only to help the folks to solve their problems and help them achieve their wishes to come through and also to get rid of black magic and evil forces. They mainly invoke deities from heavenly realm and earth realm to work on their spells / rituals. Taoist Masters enjoy the popularity and fame in the public. They walk around with the title "I Am A Taoist Master".
2) The Taoist Sorcerers
Taoist Sorcerers practice both the "Right" Path and "Left path". They help folks to solve their problems and help them achieve their wishes BUT they also can harm and destroy their own enemies or help the folks to seek revenge / punish / get even with their enemies. They invoke Deities from Heavenly Realm, Earth Realm and also seek support from 5 Ghosts, Demons from the Underworld and Ghosts , Animal Spirits , Insect Spirits from Earth Realm. They are often trained in the lineage of 茅山派 (Mao-Shan Sect) ，阴山派 (Yin-Shan Sect)，鬼山派 (Gui-Shan Sect) etc.
In olden days, a Taoist Sorcerer is an important figure in the village. Folks in the Village will seek his help regarding all kind of spiritual matters, including revenge magic on the outsiders who bullied or wronged someone from the Village, example: a girl from the village was cheated by a man from other place.
In this modern era, due to majority of modern folks who are non-believers in spiritual matters / black magic, Taoist Sorcerer often shy away from the public , or at least blend in with the public, therefore no one in the public knows he is in fact a Taoist Sorcerer (Black Magician). Being Secretive, he is often a loner, like a Taoist Wanderer. He casts spell and performs magic ritual alone, when no one is around. He mainly applies his magical knowledge for his own well-being, own benefits, personal spiritual protection and punish his own enemies. He provides the same help to his own family members and close friends. Outsiders mostly come to him /her only through word of mouth and they have to pay very high fee for his help.
Difference between Taoist Holy Masters and Taoist Sorcerers
Taoist Masters do good and give the image of "helping" the public and love the publicity. Taoist Sorcerers do good /evil for his own benefit and always low profile.
Additional Information
Taoist Magic Practitioners / Taoist Masters / Taoist Sorcerers are neither Taoist Spirits Mediums, nor Taoist Priests. In Taiwan, Taoist Masters do support and train folks who want to become Taoist Spirit Mediums. Some Taoist Masters (The Holy Ones) might want to train to become Taoist Priests someday.
Related Article: Where To Learn Taoist Sorcery?