diff --git a/nixos/doc/manual/configuration/declarative-packages.xml b/nixos/doc/manual/configuration/declarative-packages.xml
index be9884fe9dce..bf7430244545 100644
--- a/nixos/doc/manual/configuration/declarative-packages.xml
+++ b/nixos/doc/manual/configuration/declarative-packages.xml
@@ -14,9 +14,10 @@
 <programlisting>
 <xref linkend="opt-environment.systemPackages"/> = [ pkgs.thunderbird ];
 </programlisting>
-  The effect of this specification is that the Thunderbird package from Nixpkgs
-  will be built or downloaded as part of the system when you run
-  <command>nixos-rebuild switch</command>.
+  The <literal>pkgs</literal> variable is used to reference packages in your
+  root channel. The effect of this specification is that the Thunderbird
+  package from your root Nixpkgs channel will be built or downloaded as part of
+  the system when you run <command>nixos-rebuild switch</command>.
  </para>
 
  <para>
@@ -27,8 +28,10 @@ nixos.firefox   firefox-23.0   Mozilla Firefox - the browser, reloaded
 <replaceable>...</replaceable>
 </screen>
   The first column in the output is the <emphasis>attribute name</emphasis>,
-  such as <literal>nixos.thunderbird</literal>. (The <literal>nixos</literal>
-  prefix allows distinguishing between different channels that you might have.)
+  such as <literal>nixos.thunderbird</literal>. The <literal>nixos</literal>
+  prefix tells us that we want to get the package from the `nixos` channel.
+  Some systems have other channels installed, such as `nixpkgs` or custom
+  channels for development purposes.
  </para>
 
  <para>