Add diagram, thanks @lukemarsden @weaveworks <3

docs/concepts-k8s.md

@@ -196,7 +196,7 @@ Yes!
 
 - A few common resource types are:
 
-  - node (self-explanatory)
+  - node (a machine — physical or virtual — in our cluster)
   - pod (group of containers running together on a node)
   - service (stable network endpoint to connect to one or multiple containers)
   - namespace (more-or-less isolated group of things)
@@ -206,6 +206,14 @@ Yes!
 
 ---
 
+class: pic
+
+![Node, pod, container](thanks-weave.png)
+
+(Diagram courtesy of Weave Works, used with permission.)
+
+---
+
 # Declarative vs imperative
 
 - Kubernetes puts a very strong emphasis on being *declarative*