diff --git a/Doc/library/logging.rst b/Doc/library/logging.rst
index c5997ef..347c72c 100644
--- a/Doc/library/logging.rst
+++ b/Doc/library/logging.rst
@@ -734,7 +734,11 @@
 
    Provides an overriding level *lvl* for all loggers which takes precedence over
    the logger's own level. When the need arises to temporarily throttle logging
-   output down across the whole application, this function can be useful.
+   output down across the whole application, this function can be useful. Its
+   effect is to disable all logging calls of severity *lvl* and below, so that
+   if you call it with a value of INFO, then all INFO and DEBUG events would be
+   discarded, whereas those of severity WARNING and above would be processed
+   according to the logger's effective level.
 
 
 .. function:: addLevelName(lvl, levelName)