Merge pull request #6322 from tengqm/improve-kubectl-doc

Improve docs related to kubectl

docs/user-guide/kubectl-overview.md

@@ -264,6 +264,17 @@ $ kubectl describe pods <rc-name>
 $ kubectl describe pods --include-uninitialized=false
 ```
 
+**Note:** The `kubectl get` command is usually used for retrieving one or more
+resources of the same resource type. It features a rich set of flags that allows
+you to customize the output format using the `-o` or `--output` flag, for example.
+You can specify the `-w` or `--watch` flag to start watching updates to a particular
+object. The `kubectl describe` command is more focused on describing the many
+related aspects of a specified resource. It may invoke several API calls to the
+API server to build a view for the user. For example, the `kubectl describe node`
+command retrieves not only the information about the node, but also a summary of
+the pods running on it, the events generated for the node etc.
+{: .note}
+
 `kubectl delete` - Delete resources either from a file, stdin, or specifying label selectors, names, resource selectors, or resources.
 
 ```shell