+## internal pages and `aggregateinternal`
+
+This plugin creates a page for each aggregated item.
+
+If the `aggregateinternal` option is enabled in the setup file (which is
+recommended), aggregated pages are stored in the source directory with a
+"._aggregated" extension. These pages cannot be edited by web users, and
+do not generate first-class wiki pages. They can still be inlined into a
+blog, but you have to use `internal` in [[PageSpecs|IkiWiki/PageSpec]],
+like `internal(blog/*)`.
+
+For backward compatibility, the default is that these pages have the
+".html" extension, and are first-class wiki pages -- each one generates
+a separate HTML page in the output, and they can even be edited.
+
+That turns out to not be ideal for aggregated content, because publishing
+files for each of those pages is a waste of disk space and CPU, and you
+probably don't want to allow them to be edited. So, there is an alternative
+method that can be used (and is recommended), turned on by the
+`aggregateinternal` option in the setup file.
+
+If you are already using aggregate and want to enable `aggregateinternal`,
+you should follow this process: