These pages are used to show the full items, all comments that were made and a form to add comments.
Very basic buildup for a detailed item page:
<html>
<head>
<title>My Weblog :: Item</title>
</head>
<body>
<h1>Item</h1>
<%item(detailed)%>
<h1>Comments</h1>
<%comments(detailed)%>
<h1>Add Comment</h1>
<%commentform%>
</body>
</html>
This will show the item and comments using the 'detailed' template, and add a standard commentform.