diff --git a/content/en/docs/concepts/api-extension/custom-resources.md b/content/en/docs/concepts/api-extension/custom-resources.md
index f65985e474..624fbc83b3 100644
--- a/content/en/docs/concepts/api-extension/custom-resources.md
+++ b/content/en/docs/concepts/api-extension/custom-resources.md
@@ -28,7 +28,12 @@ Once a custom resource is installed, users can create and access its objects wit
 ### Custom controllers
 
 On their own, custom resources simply let you store and retrieve structured data.
-It is only when combined with a *controller* that they become a true [declarative API](/docs/concepts/overview/working-with-objects/kubernetes-objects/#understanding-kubernetes-objects). The controller interprets the structured data as a record of the user's desired state, and continually takes action to achieve and maintain that state.
+It is only when combined with a *controller* that they become a true declarative API.
+A [declarative API](/docs/concepts/overview/working-with-objects/kubernetes-objects/#understanding-kubernetes-objects)
+allows you to _declare_ or specify the desired state of your resource and tries
+to match the actual state to this desired state.
+Here, the controller interprets the structured data as a record of the user's
+desired state, and continually takes action to achieve and maintain this state.
 
 A *custom controller* is a controller that users can deploy and update on a running cluster, independently of the cluster's own lifecycle. Custom controllers can work with any kind of resource, but they are especially effective when combined with custom resources. The [Operator](https://coreos.com/blog/introducing-operators.html) pattern is one example of such a combination. It allows developers to encode domain knowledge for specific applications into an extension of the Kubernetes API.