Registration - answering the questions

Vocal registers are both vital to understanding the voice and something every voice teacher and singer does not always agree on. How many are there? What are they? Should they be taught? The answers: many, there are two types of registers - laryngeal and acoustic, and I imagine every voice teacher teaches registers whether they know it or not. Often when a teacher models for a student what they are demonstrating is proper registration, as much as any other feature of their singing.