In cases when you don't want to care about the heading level (1 to 6), you can use the Generic Heading:

[heading Heading]

The Generic Heading assumes the level, plus one, of the innermost section where it is placed. For example, if it is placed in the outermost section, then, it assumes h2.

Headings are often used as an alternative to sections. It is used particularly if you do not want to start a new section. In many cases, however, headings in a particular section is just flat. Example:

[section A]
[h2 X]
[h2:link_id Y]
[h2 Z]
[endsect]

Here we use h2 assuming that section A is the outermost level. If it is placed in an inner level, you'll have to use h3, h4, etc. depending on where the section is. In general, it is the section level plus one. It is rather tedious, however, to scan the section level everytime. If you rewrite the example above as shown below, this will be automatic:

[section A]
[heading X]
[heading Y]
[heading Z]
[endsect]

They work well regardless where you place them. You can rearrange sections at will without any extra work to ensure correct heading levels. In fact, with section and heading, you have all you need. h1..h6 becomes redundant. h1..h6 might be deprecated in the future.