These crawls are part of an effort to archive pages as they are created and archive the pages that they refer to. That way, as the pages that are referenced are changed or taken from the web, a link to the version that was live when the page was written will be preserved.
Then the Internet Archive hopes that references to these archived pages will be put in place of a link that would be otherwise be broken, or a companion link to allow people to see what was originally intended by a page's authors.
This is a collection of pages and embedded objects from WordPress blogs and the external pages they link to. Captures of these pages are made on a continuous basis seeded from a feed of new or changed pages hosted by Wordpress.com or by Wordpress pages hosted by sites running a properly configured Jetpack wordpress plugin.