Added detail per issue #3425

docs/eventing/channels/_index.md

@@ -7,11 +7,27 @@ aliases:
   - /docs/eventing/channels/default-channels
 ---
 
-Channels are Kubernetes [custom resources](https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/) that define a single event forwarding and persistence layer.
+An event might be relevant to many consumers. One way to handle this is to directly tie each consumer
+to the producer that creates the event, making a fan-out pattern.
 
-A channel provides an event delivery mechanism that can fan-out received events, through subscriptions, to multiple destinations, or sinks. Examples of sinks include brokers and Knative services.
+This fan-out pattern, however, introduces complex problems for the application architecture, such as
+retries, timeouts, and persistence. Instead of burdening the producer with these problems, you can
+use channels.
 
-<img src="images/channel-workflow.png" width="80%">
+A channel is a Kubernetes [custom resource](https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/) that defines a single event forwarding and persistence layer.
+
+Channels function as event delivery mechanisms that can fan out received events, through
+subscriptions, to multiple destinations, referred to as sinks. Examples of sinks include brokers and
+Knative services.
+
+<img src="images/channel-workflow.png" width="80%"><br>
+
+There are several kinds of channels, but they all make it possible to deliver events to all relevant
+consumers and, importantly, make the events persist.
+
+When you create a channel, you can choose which kind of channel is most appropriate for your use
+case. For development use cases, an in-memory channel might suffice, but for production persistence,
+you might need retry and replay capabilities.
 
 ## Next steps