change "finding distributions" docs to correctly describe index and find-links behaviour

src/zc/buildout/buildout.txt

@@ -2222,11 +2222,24 @@ Finding distributions
 ---------------------
 
 By default, buildout searches the Python Package Index when looking
-for distributions. The `find-links` options allows the addition of
-more locations to search and is used extensively in this
-documentation. 
+for distributions. You can, instead, specify your own index to search
+using the `index` option::
 
-These can be urls::
+  [buildout]
+  ...
+  index = http://index.example.com/
+
+This index, or the default of http://pypi.python.org/simple/ if no
+index is specified, will always be searched for distributions unless
+running buildout with options that prevent searching for
+distributions. The latest version of the distribution that meets the
+requirements of the buildout will always be used.
+
+You can also specify more locations to search for distributions using
+the `find-links` option. All locations specified will be searched for
+distributions along with the package index as described before. 
+
+Locations can be urls::
 
   [buildout]
   ...
@@ -2238,13 +2251,13 @@ They can also be directories on disk::
   ...
   find-links = /some/path
 
-Finally, direct paths to distributions can be specified::
+Finally, they can also be direct paths to distributions::
 
   [buildout]
   ...
   find-links = /some/path/someegg-1.0.0-py2.3.egg
 
-You can also specify more than one place to look::
+Any number of locations can be specified in the `find-links` option:: 
 
   [buildout]
   ...
@@ -2253,12 +2266,6 @@ You can also specify more than one place to look::
       /some/otherpath
       /some/path/someegg-1.0.0-py2.3.egg
 
-In this case, distribution sources are searched in the order
-specified. In the event that a distribution cannot be found in any of
-the locations specified, the python package index will still be
-searched unless other buildout configuration options have prevented
-this.
-
 Dependency links
 ----------------