There are examples below that statement for common usage, but if you want a deeper understanding:

    tag.xyz %
       property = value
       child1
       child2

Will produce the data structure:

    {tags = {"tag", ".xyz"}
     props = {property = value}
     children = {child1, child2}}

as an instance of the ENode class. Then, transformer functions can process the data structure to generate HTML or other things, e.g.

    require: /html
    html(thing)
    ==> <tag class="xyz" property="value">child1child2</tag>