Amateurs are taught the proper use of their voice so that they don't get tired and they don't damage it. They are instructed in such a way to promote all the good elements they have. Vocal training workout, practice with repertory of their choice.
For professionals of any style of music there is special training for improving (or re-gaining) of their technique as well as correcting any errors. Responsible guidance.
At classical singing courses all technical demands of the kind are covered and students take exams according to the regulations of the Greek Ministry of Civilization.
For speakers (executives, lawyers, actors, teachers, sales persons etc) there is a special voice training for helping them heal, free and empower their voice, in order to become more charismatic, confident, powerful and influential.