Calling Mercury Functions from Your Own Pages
In a Mercury site every page is a Mercury page unless it is served from a folder that explicitly has URL rewriting disabled. As such every page has access to both the m( ) and the d( ) functions and can therefore call any of the functions or display files within the entire Mercury system, automatically taking overrides into consideration.
If you want to build a page called html/about-us.php and you want to call a Mercury function (maybe to load a jQuery file or to leverage a display shortcut) then you can just build the file as you have conventionally done and you can use the Mercury calls. Remember that your standalone page will still be sucked into the layout.php file unless you change how it is handled (see Layouts).
For that matter, you could create a file called about-us.html and do all of the same. Even though the file has an html extension is it still being included by the Mercury PHP framework and anything within the file that is written as PHP will still be executed.
What Can You Call?
From your standalone pages you can call any of the functions listed in the Important Mercury Functions documentl, and a few more. 99+% of the time the functions listed will be the ones you use. Most of what you call will be m( ) and d( ).