Contact allows system users to assign a contact for an event.
Edit
To add a contact for an event go to Administration -> Apps -> Modules -> Events.
1. Select the appropriate instance and either select the required event or Add a new event.
2. Select Contact. The following view will be presented:
3. Select the appropriate option.
Note: Defined exposes fields allowing manual population of contact information.
Easysite user allows selection from a list of users.