Unlike mage knights and mage smiths, a mage tech (or technician or witch) is a mage who focuses their energies on using skilled work with magic. This includes artists, investigators, telepathic network operators, and other skills that frequently require a degree of training and knowledge.
Techs make up the majority of the mages since knights have a more dangerous careers and smiths require a great deal of energy in addition to needing an attention to detail. There are some circles that feel a smith is only a category of techs, but most feel the channeling and imbuing of energy is a drastically different set of skills than shaping energy.