Feeds contain feed items, or individual posts published by the site providing the feed. Feeds may be grouped in categories, generally by topic. Users view feed items in the <a href="@aggregator">main aggregator display</a> or by <a href="@aggregator-sources">their source</a>. Administrators can <a href="@feededit">add, edit and delete feeds</a> and choose how often to check each feed for newly updated items. The most recent items in either a feed or category can be displayed as a block through the <a href="@admin-block">blocks administration page</a>. A <a href="@aggregator-opml">machine-readable OPML file</a> of all feeds is available. A correctly configured <a href="@cron">cron maintenance task</a> is required to update feeds automatically.