diff --git a/xep-0389.xml b/xep-0389.xml
index 49cd178f..923578aa 100644
--- a/xep-0389.xml
+++ b/xep-0389.xml
@@ -117,6 +117,38 @@
+
+
+
+ - Challenge
+ -
+ A challenge is an action taken during account registration or recovery
+ that requires a response.
+ For example, displaying a form to a user or asking for a token.
+
+
+
+ - Challenge Type
+ -
+ The type of a challenge is a unique string that identifies the type of
+ payload that can be expected.
+ For example, a challenge element with type "jabber:x:data" can be
+ expected to contain a data form.
+ Challenge types must be defined and registered in the challenge types
+ registry.
+ When defining a challenge it is often convenient to reuse an XML
+ namespace from the document defining the challenge.
+
+
+
+ - Flow
+ -
+ A flow, or more specifically a "registration flow" or "recovery flow",
+ is an ordered collection of challenges.
+
+
+
+