They can be any sort of event: collectors' fair, potfest, exhibitions, auctions, whatever, so long as they cover pottery and collectables.
To add your event, click the Calendar link on the blue menu bar above, go the date your event is due to start, click the date and this will open up a modified version of the normal posting screen with the extra bits to make the calendar link. Make sure you select the correct start date from the drop down month and date list and tell us how many days the event will run for (there's a dropdown selector for this too.)
Once this is done, complete the rest of the topic as normal, save it and the topic will appear in full in the What's On forum, on the Calendar screen, and in the list of upcoming events on the board index. (This shows events up to 60 days ahead.)
Now you have no excuse to not know what's going on.