The JEvents tags addon allows you to tag your events i.e. to attach keywords to your events. 

This means that you can filter your menu items and modules to show events matching certain tags and also to filter/search for events using the filter events module. 

Using the Matching Events addon you can show a list of events that match your event in the event detail page.

The addon can be configured so that your event creators can create tags as they create the underlying events.