A “link” tag defines a URL of some other related page. It does not display anything or cause anything to happen by itself, it’s just metadata defining some other related page.
The “rel” attribute defines the relationship of that page to this one.
There are a lot of possible “rel” values that are in common use.
The rel=”archives” does not have any specific use that I am aware of. It is used to define other pages that are archives of the site in question. In other words, it’s defining pages where the content on this page will be seen in the future.
To create the archive links in your own page, add this to your theme’s header.php file:
<?php wp_get_archives('type=monthly&format=link'); ?>
Or if you prefer something other than monthly, change that.
There’s lot more rel types as well:
The rel=”stylesheet” defines the location of a stylesheet for the current page.
The rel=”alternate” defines alternate versions of this page. This is most often used to define locations of RSS feeds for the current page.
The rel=”pingback” is used to define a location for the pingback mechanism to work when blogs ping each other.
The rel=”EditURI” defines the location of a RPC connector for the XML-RPC mechanism, for remote editing of the page.
The rel=”microsummary” defines the location of a short summary or list of summaries that would apply to the current page. Firefox can use these in its bookmarks functionality.
The rel=”openid” stuff is used to define OpenID variables for the OpenID protocol.
And so on. There’s more, but these are the most commonplace ones.
