They are special superset numbers that are sometimes perfect for footnotes. Here they are:
¹ ² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹
I generally prefer to superscript the number myself, like:
<p>This next word<sup>1</sup> has a footnote.</p>
You’d probably add an anchor link around that as well to link to an ID elsewhere on the page that explains the footnote.
But sometimes it just isn’t practical or possible to use HTML as you author a bit of text. As I type, I’m writing in the WordPress Gutenberg editor. I can write in HTML block if I want, but it’s much more practical to use the default paragraph blocks, which have options for stuff like bold, italic, and strikethrough, but not for superscript. I don’t really wanna convert a block to HTML just to use a superscript number. So, a special Unicode character¹ it is.
- Another thing the Gutenberg editor can’t do is add an ID to a link, so it’s not really practical for me to offer a “jump back to the footnote” link down here. Sad face.