With the "per teacher" licensing model, you need a license for each teacher/tutor (session host) who will hold online classes and live sessions.
Each teacher is provided with his own virtual classroom with independent scheduling. The administration can configure the teacher with scheduling access as well as access to your students.
This licensing model is suitable if you have several teachers (or session hosts) and you want to allow all of them to be able to run live classes at any time, each one in a his own virtual classroom.
The teacher licenses are transferrable, which means that you can transfer the license of a retired teacher to another person. You can also use generic (neutral) teacher names.