Let’s say you have a markdownify shortcode.
Usecase 1
markdownify.html:
## Heading
{{ .Inner | markdownify }}
The | markdownify part is important now!
{{< markdownify >}}
Paragraph.
{{< /markdownify >}}
Usecase 1 renders your paragraph to HTML—but not the heading in your shortcode file itself.
Usecase 2
markdownify.html:
## Heading
{{ .Inner }}
You do not need markdownify here.
{{% markdownify %}}
Paragraph.
{{% /markdownify %}}
In usecase 2 the heading will be sent to the content renderer—that is it will be rendered to HTML and e.g. part of the TOC.