Clarification on Azure Event Grid System Topics and what they handle

I am trying to get my mental picture right about how Event Grid System Topic works.

Is it "correct" to say that when you create a system topic, then that the topic may handle ALL the events from the selected Azure Service? Meaning that all events will pass through this system topic?

And that it is then up to the individual subscriptions on that topic, to filter out what events you want to receive?

I understand the system topics are managed by Azure and what's inside is "hidden" but I want to know if my mental model and understanding of them is correct or not?

Or does the system topic only handles the union of all the events that the subscriptions are asking for? To not having to send all events through the topic?

Only Azure services can publish events to system topics, which then forward the events to the topic's subscribers that receive and process them. We cannot view events in an Event Grid System Topic without creating an event subscription, which acts as emit events for resources across the subscription.

No, the events will not be sent to the underlying Azure Service without system subscriptions since there is no connection/endpoint established between the subscription and the topic. An Event Grid System Topic must have an Event Subscription because, without subscriptions, there is no connection endpoint to receive and send events to the underlying Azure Service.

I followed these links to create System topics and Event Subscriptions in Azure Event Grid.

• Go to the Azure Portal => Select services from the left menu where you want to add an Event Subscription => Search for Events and click on + Event Subscription.

• On the Create Event Subscription page, provide the following details like Name, System Topic Name, event types, and specify endpoint details like Endpoint type and Additional Features (Optional).

Endpoint: Enter the endpoint URL or select an endpoint type from the list of supported event handlers (e.g., Azure Function, Logic App, Webhook).

Once all configurations are complete, click Create to finalize the setup.

Based on the filter type selected and the action on the resource through which the event is configured, it will trigger the events in the Event Subscription and send them to the endpoint.