This is a list of pages with broken file links or transclusions with non existent files. These pages should be checked to make sure that all missing files are either uploaded, or the links fixed to files that actually do exist.
To remove a page off the list, you must fix all of the broken file links, after which the page will not have this category after the next edit is made. If there are no broken file links then edit the page and add or remove content to the page. This will remove the category from the page automatically.