Update api.rst (#812)

Joey5337 · web-flow · commit 56c410cda07f · 2020-04-19T14:44:44.000+12:00
Clarification for Notifier docs
diff --git a/doc/api.rst b/doc/api.rst
@@ -33,7 +33,7 @@ Utilities
 Notifier
 --------
 
-The Notifier object is used as a message distributor for a bus.
+The Notifier object is used as a message distributor for a bus. Notifier creates a thread to read messages from the bus and distributes them to listeners.
 
 .. autoclass:: can.Notifier
     :members:
