Register/Get sidebar?

I can’t quite seem to figure out how it works.

By default i have a sidebar in sidebar.php that i load using get_sidebar();. That works great (no need to register it), but i have a custom page template for another page where i want to load another sidebar. I know i can use include(‘filename’) to load it but i assume there is some sort of wordpress way to do it as well.

I know i have to register the new sidebar in the functions.php file, but where do i actually reference the sidebar file?

From the doc:

name - Sidebar name (default is localized 'Sidebar' and numeric ID).
id - Sidebar id - Must be all in lowercase, with no spaces (default is a numeric auto-incremented ID).
description - Text description of what/where the sidebar is. Shown on widget management screen. (Since 2.9) (default: empty)
class - CSS class name to assign to the widget HTML (default: empty).
before_widget - HTML to place before every widget(default: '<li id="%1$s" class="widget %2$s">') Note: uses sprintf for variable substitution
after_widget - HTML to place after every widget (default: "</li>n").
before_title - HTML to place before every title (default: <h2 class="widgettitle">).
after_title - HTML to place after every title (default: "</h2>n").

In neither of those preferences do you specify the filename of the sidebar, so how do i do it?

After i have registered it successfully, i assume i can load it using get_sidebar(ID);, will that work?

Any help is very appreciated!