Raised and lowered digits and signs — for squares, formulas and footnotes.
Superscript and subscript characters let you write things like x², m³, the ⁿ in an exponent, or the subscripts in a chemical formula such as H₂O and CO₂ — in plain text, without any special formatting. That makes them handy in spreadsheet headers, social posts, filenames and chat, where you can't apply true superscript styling. They're a fixed set of precomposed characters, so only the digits and a few signs exist; for arbitrary raised text in a document, your editor's actual superscript/subscript formatting (Ctrl/Cmd+Shift+= and +,) is the better tool. The trademark (™), registered (®) and degree (°) marks are the most-copied of the bunch.