There are two ways to view events from other calendars in Teamup: Import via CSV file or sync via iCalendar feed.
These two methods are very different:
Importing via CSV is a one-time transfer of data from a third-party application to Teamup. It does not offer ongoing synchronization.
Inbound iCalendar feeds provides an active one-way synchronization, meaning that Teamup periodically fetches the latest feed content and updates the calendar.