Add explanatory comment for annotation box example

mollyrossow · mollyrossow · commit 1b303a133f5a · 2019-01-11T12:36:46.000-06:00
diff --git a/examples/text_labels_and_annotations/demo_annotation_box.py b/examples/text_labels_and_annotations/demo_annotation_box.py
@@ -3,7 +3,12 @@
 Demo Annotation Box
 ===================
 
+The AnnotationBbox Artist creates an annotation on some location using an
+OffsetBox. This example demonstrates three different OffsetBoxes: TextArea,
+DrawingArea and OffsetImage. AnnotationBbox gives more fine-grained control
+than using the axes method annotate.
 """
+
 import matplotlib.pyplot as plt
 import numpy as np
 
