Event data describes actions performed by entities, also known as actors. Event data has three key pieces of information: actor, timestamp, and state.
Actor is the person or thing generating the event.
The timestamp is the point in time at which the event happened.
The state is the other relevant information about the event, including information about actors related to the event.
In the above example, userid is the Actor, timestamp is the time the event happened and event, region & age are the state that further define the event.