Docs: reformat merger and executor config docs

Change-Id: I75e67a592cdef5fcf4a2576cd5a5814cb79211f8
diff --git a/doc/source/glossary.rst b/doc/source/glossary.rst
index 98bee10..6c8a4b4 100644
--- a/doc/source/glossary.rst
+++ b/doc/source/glossary.rst
@@ -45,6 +45,27 @@
       might leave feedback in a remote system on a proposed change,
       send email, or store information in a database.
 
+   trusted execution context
+
+      Playbooks defined in a :term:`config-project` run in the
+      *trusted* execution context.  The trusted execution context has
+      access to all Ansible features, including the ability to load
+      custom Ansible modules.
+
+   untrusted execution context
+
+      Playbooks defined in an :term:`untrusted-project` run in the
+      *untrusted* execution context.  Playbooks run in the untrusted
+      execution context are not permitted to load additional Ansible
+      modules or access files outside of the restricted environment
+      prepared for them by the executor.  In addition to the
+      bubblewrap environment applied to both execution contexts, in
+      the untrusted context some standard Ansible modules are replaced
+      with versions which prohibit some actions, including attempts to
+      access files outside of the restricted execution context.  These
+      redundant protections are made as part of a defense-in-depth
+      strategy.
+
    untrusted-project
 
       One of two types of projects which may be specified by the