The discussion forum module for expression engine uses {include:file} tags in its templates like in forum\_themes/developer/forum\_index/main\_forum\_list.html:

```
{include:table_heading}
{include:table_rows}
{include:table_footer}

```

I've searched for the include tag documentation but I can't find it anywhere? What is the include tag and when/where should it be used? Is it specific to the discussion forum module?