Sometimes one needs some tag in a page template just for the logic (i.e. to define variables inside of a tal:repeat loop, but do not really need a separate html-tag in the layout.

One possibility is to use tal:omit-tag="" inside the tag, which executes the tal: statements but does not render the tag, only its contents.

However an easier way to achive this is to name the tag <tal:block> ; in this case the element is not rendered, and one can even skip the tal: prefix to the tal statement. This also has the advantage one can clearly see the tag is just needed for the logic.

Thus instead of:

<span tal:omit-tag="" tal:define="foo container/bar">...</span>

one can write:

<tal:block define="foo container/bar">...</tal:block>

You do not even have to name the tag <tal:block> ; <tal:def> or <tal:x> would do as well. However <tal:block> seems to work best with some WYSIWYG editors, and is just very common in use.