Each element, its component parts, and elements it contains must be explicitly tagged. For example, here is the formal markup for a chapter head. To read this, and other markup examples easily, tags are indented. Indentation is not required in actual markup.
<chaphead> <head> <partext>Front Panel Help</partext> </head> </chaphead>
Notice the additional tags, <head> and <partext>; these are subcomponents of the <chaphead> element. Each of these elements requires an explicit start and end tag.