What is a booker?
A booker is essentially a client facing calendar that a visitor can use to book an appointment with you.
It's possible to have multiple calendars linked to a single booker and you can have calendars linked to several different bookers.
E.g. Paul, Tom and Fred are 3 sales people.
They each have their own calendars linked to the platform.
They want to have individual "Calendars" and a shared "Calendar" that people can book appointments on.
These "Calendars" are called bookers.
For the scenario above, you'd want to create 3 individual bookers and 1 team booker.