If you want to add categorisation to the events in your platform, you can set event types via de taxonomies. /admin/structure/taxonomy/manage/event_types/overview
When the event types are enabled, your users can choose from them while creating or editing an event.
In the event overview and on the events tab on profile a filter is present to search for specific type of events.
As a site manager you can choose wether you want to make the event type field mandatory for users to choose from. This can be done via the event type setting in the dashboard or /admin/config/opensocial/event-type