📜 Docs: expand glossary with new event definitions and clarify existing terms

Author: tyler-dane

docs/learn/glossary.md

@@ -2,10 +2,22 @@
 
 Definition of terms used in the source code and documentation.
 
-**Event**: A calendar event that is already persisted to the database and is not being edited. When a user first views the calendar, the events they see are Events.
+## Events
+
+**Standalone Event**: An event that has a datetime and is NOT recurring.
+
+**Grid Event**: An event that is assigned to a specific time slot on the calendar in the grid.
 
 **Draft Event**: A calendar event that has pending changes that have not yet been persisted to the database. When a user makes changes to an event in the form, or drags the event, or resizing its times, the user is operating on a draft event. After the user clicks "Save", the draft event is persisted to the database, and the Draft Event goes away and is replaced with the Event.
 
+**Someday Event**: These have `startDate` and `endDate` like regular timed events, but they have not yet been assigned to a specific time slot on the calendar in the grid. Instead, they are stored in the sidebar. These may be recurring or standalone.
+
+**Base Event**: A _recurring_ event that is recurring and has the series `RRULE` in the `recurrence` field.
+
+**Instance Event**: A _recurring_ event that is an instance of the base event.
+
+## Other
+
 **Calendar**: A calendar is a collection of events. It is the main object in the application.
 
 **Calendar List**: AKA sub-calendars. A calendar list is a collection of calendars.
@@ -18,5 +30,4 @@ Definition of terms used in the source code and documentation.
 - Month view
 - Year view
 
-
-**Sync**: The Compass feature that allows users to sync their calendar data with other calendars like Google Calendar.
+**Sync**: The Compass feature that allows users to sync their calendar data with other calendars like Google Calendar.