What does linking paid sessions to a calendar event do?
When creating an event on the calendar, you are given the option to associate the event with a specific paid session.
Linking the session is completely optional. If you do end up linking a session, when parents view the event they will be presented with an easy to use registration button.
If you are using your team's public calendar (url available under Settings -> Team) the public calendar will also show a link for people to easily register for the session associated with the event.