Glyph
A glyph is the shape you see; a character is the encoded idea behind it. One character can be drawn as several different glyphs.
See it
What it is
A glyph is the visible shape a font uses to render text. A character is the abstract encoded item, such as Unicode U+0061 LATIN SMALL LETTER A; a glyph is the particular drawing of that `a` in Garamond, Inter, or another font. One character can have several glyphs, and one ligature glyph can represent several characters.
Reach for the word when discussing alternate letterforms, ligatures, contextual substitutions, icon fonts, or a missing-character box. It lets you separate what the text says from the shape selected to display it. OpenType layout can swap glyphs without changing the underlying character sequence. That missing-character box has a name of its own, tofu, and Google named the Noto project after the goal of no more tofu: a glyph for every character in Unicode.
The gotcha is that an outline is not text. Converting type to SVG paths preserves glyph shapes but discards the characters a browser needs for search, selection, copy and paste, and screen-reader output. Keep live text whenever those behaviors matter.
Ask AI for it
Build an interactive glyph inspector for the text `office affine`. Keep the source as live HTML text and show each Unicode code point underneath it. Add controls for CSS font-feature-settings values `'liga' 1`, `'liga' 0`, `'salt' 1`, and `'ss01' 1`, disabling any control the loaded font does not support. Explain when several characters become one ligature glyph, but never replace the accessible text with SVG paths. Include a copy button that proves the underlying character string remains unchanged.