The paradigm of event-based communication revolves around a publisher-subscriber model where a sender broadcasts a message that one or more receivers capture.
Events get sent whether or not receivers are listening, and receivers don’t acknowledge it when they receive an event.
Event-based communication takes place near-real time.
Components of Event-Driven Systems
Event
A change in state that is meaningful in a business process.
Event message
A message that contains data about the event.
Event producer
The publisher of an event message
Event channel
A stream of events on which an event producer sends event messages and event consumers read those messages.
Event consumer
A subscriber to a channel that receives messages from the channel.
Event bus
A communication and storage service that enables event streaming using the publish-subscribe model. The event bus enables the retrieval of stored event messages at any time during the retention window.

Advantages of Event Driven Architecture
Unlike request-response communication models, event-driven model decouples event producers from event consumers, simplifying the communication model in connected systems.
We don’t have to make any request to a server to obtain information about a certain state.
Instead, a system subscribes to an event channel and is notified whenever new states occur.
Any number of consumers can receive and react to the same events.
When to Use Platform Events:
Platform to External App
External App to Platform App
Platform to Platform
Please check below video for detailed explaination: