Basics

The argument is the URL and the content is the label:

The directives reference

A button with no content at all shows its target instead of an empty button, which is what makes a one-line .. button-link:: worth writing:

https://docutils.sourceforge.io/rst.html

The label is parsed as inline markup — the only other place this build does that with a directive's argument or content is a dropdown's title:

Read conf.py carefully

A label may run over several lines. They are joined the way docutils joins them, so this is one label and not two:

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