Where Wikipedia uses large amounts of content from public-domain sources, it is appropriate to use one of these templates to note the source. This is not required by copyright law, but it is an accepted method of avoiding plagiarism. See WP:Plagiarism.
To include a template in this category, add [[Category:Attribution templates]] to the <includeonly> section at the bottom of the template's /doc subpage if such a page exists. Otherwise, add <noinclude>[[Category:Attribution templates]]</noinclude> to the end of the template code, making sure it starts on the same line as the last character of the code.