What are the "Simple" views in the Calendar?
Simple views are versions of the Day and Week tabs which don't have a time scale beside them. These views do not line up the event with its start and end time but rather show events in more of a list (even though it's a portal).
These views are a little faster than the timed views. And, if you have a ton of overlapping events they can offer more clarity without requiring you to filter the calendar.
The default set of views (simple v regular) is set in the "Load Calendar Settings - On Startup" script, towards the end, right after the comment "Use Simple Views?".
Once the system is up, the preferred view is up to the user and some users can be on simple view while others are on regular ones. Users can flip between simple and regular views on the Settings tab.