EventBridge accepts events from many different event sources, including over 200 AWS services, custom events from your Lambda functions or applications, and third-party SaaS applications. You specify an action to take when EventBridge receives an event that matches the event pattern in the rule. When an event matches, Amazon EventBridge sends the event to the specified target and triggers the action defined in the rule.

To route events from these sources to the correct target, the events must be placed on a corresponding event bus. There are three types of event buses. The first type is the default bus, which is always available in every account, and it’s where AWS events are routed to. The second type is a custom event bus. You can create custom event buses for your own applications to meet your business needs. Lastly, you can also create SaaS event buses, which are created when you configure SaaS applications as an event source.

There are many potential event targets. Event targets are what the event bus route to once a corresponding event happens. Targets include AWS Lambda, Amazon Kinesis, AWS Step Functions, Amazon API Gateway, and even event buses in other accounts. This flexible design allows you to create a wide variety of integration patterns based on your specific needs.

https://aws.amazon.com/blogs/compute/building-an-event-driven-application-with-amazon-eventbridge/