diff --git a/src/callbacks.py b/src/callbacks.py
index 146a37faf..697f0c144 100644
--- a/src/callbacks.py
+++ b/src/callbacks.py
@@ -1294,8 +1294,14 @@ class PluginRegexp(Plugin):
     list) attribute "regexps".
     """
     flags = re.I
+    # 'regexps' methods are called whether the message is addressed or not.
     regexps = ()
+    # 'addressedRegexps' methods are called only when the message is addressed,
+    # and then, only with the payload (i.e., what is returned from the
+    # 'addressed' function.
     addressedRegexps = ()
+    # 'unaddressedRegexps' methods are called only when the message is *not*
+    # addressed.
     unaddressedRegexps = ()
     Proxy = SimpleProxy
     def __init__(self, irc):