Scomps
Screen components for when tags and included templates are not enough and programming is needed.
Scomps add logic to templates or generate HTML/javascript constructs that are too difficult for templates. A good example is the menu scomp which implements the menu, including sub menus and highlighting of the current menu item.
Scomps have the same syntax as tags:
{% scompname arg=value ... %}.
Scomps are implemented by modules, tags are implemented by the template system.