This style maps your text onto Unicode's "Mathematical Fraktur" block, based on the historic Fraktur blackletter typeface used across German-language printing for centuries and still recognizable today from metal band logos and gothic branding. Fraktur ended up in Unicode's math section, not a typography section, because it was first needed to distinguish certain mathematical notations rather than for general styling — a side effect this tool takes advantage of. Five uppercase letters — C, H, I, R, and Z — use older, separately standardized Unicode symbols instead of the newer block, since those exact glyphs already existed in Unicode before the fraktur block was finalized, so this tool maps them to the correct legacy code points for visual consistency.
It's the same visual tradition — Fraktur blackletter — represented as genuine Unicode characters rather than a downloadable font file, so it displays consistently as text rather than needing a specific typeface installed.
Mathematicians occasionally needed to distinguish a fraktur-styled variable from a regular one in formulas, so Unicode standardized the full fraktur alphabet as part of its mathematical alphanumeric symbols range — general decorative use came later as a side effect.
Mostly yes on modern devices, but because it's a less common Unicode block than basic Latin, a few older phones or minimalist fonts may show some fraktur letters as blank boxes.