Reference glossary definitions in “Connect a Front End to a Back End Using a Service” (#12706)

* Reference terms in glossary

* Enable syntax highlighting for shell snippets

content/en/docs/tasks/access-application-cluster/connecting-frontend-backend.md

@@ -8,14 +8,15 @@ weight: 70
 
 This task shows how to create a frontend and a backend
 microservice. The backend microservice is a hello greeter. The
-frontend and backend are connected using a Kubernetes Service object.
+frontend and backend are connected using a Kubernetes
+{{< glossary_tooltip term_id="service" >}} object.
 
 {{% /capture %}}
 
 
 {{% capture objectives %}}
 
-* Create and run a microservice using a Deployment object.
+* Create and run a microservice using a {{< glossary_tooltip term_id="deployment" >}} object.
 * Route traffic to the backend using a frontend.
 * Use a Service object to connect the frontend application to the
   backend application.
@@ -47,13 +48,13 @@ file for the backend Deployment:
 
 Create the backend Deployment:
 
-```
+```shell
 kubectl create -f https://k8s.io/examples/service/access/hello.yaml
 ```
 
 View information about the backend Deployment:
 
-```
+```shell
 kubectl describe deployment hello
 ```
 
@@ -99,7 +100,8 @@ Events:
 The key to connecting a frontend to a backend is the backend
 Service. A Service creates a persistent IP address and DNS name entry
 so that the backend microservice can always be reached. A Service uses
-selector labels to find the Pods that it routes traffic to.
+{{< glossary_tooltip text="selectors" term_id="selector" >}} to find
+the Pods that it routes traffic to.
 
 First, explore the Service configuration file:
 
@@ -110,7 +112,7 @@ that have the labels `app: hello` and `tier: backend`.
 
 Create the `hello` Service:
 
-```
+```shell
 kubectl create -f https://k8s.io/examples/service/access/hello-service.yaml
 ```
 
@@ -137,7 +139,7 @@ the Service uses the default load balancer of your cloud provider.
 
 Create the frontend Deployment and Service:
 
-```
+```shell
 kubectl create -f https://k8s.io/examples/service/access/frontend.yaml
 ```
 
@@ -161,7 +163,7 @@ so that you can change the configuration more easily.
 Once you’ve created a Service of type LoadBalancer, you can use this
 command to find the external IP:
 
-```
+```shell
 kubectl get service frontend --watch
 ```
 
@@ -189,8 +191,8 @@ cluster.
 The frontend and backends are now connected. You can hit the endpoint
 by using the curl command on the external IP of your frontend Service.
 
-```
-curl http://<EXTERNAL-IP>
+```shell
+curl http://${EXTERNAL_IP} # replace this with the EXTERNAL-IP you saw earlier
 ```
 
 The output shows the message generated by the backend: