It’s a sort of a dynamic snippet coupled with a regex keybinding. The captured text from the regex keybinding is passed to a very generic snippet that does the inserting. The snippet itself lives in the XML package:
<!-- General HTML tags -->
<binding key="/(?i:abbr|acronym|address|applet|area|b|base|big|blockquote|caption|center|cite|col|colgroup|cote|dd|del|dfn|div|dl|dt|em|fieldset|font|form|frame|frameset|h1|h2|h3|h4|h5|h6|i|ins|kbd|label|legend|li|link|map|noframes|object|ol|optgroup|p|pre|samp|select|small|span|strong|sub|sup|table|tbody|td|textarea|tfoot|th|thead|title|tr|tt|u|ul|var)/,tab" command="insertSnippet 'Packages/XML/tag.sublime-snippet' $1">
<context name="selector" value="text.html - source - meta.tag, punctuation.definition.tag.begin, meta.scope.between-tag-pair.html"/>
</binding>