In typography, a glyph is a specific shape or design used to represent a character. Meaning, a glyph can represent a single character in a multitude of ways depending on how its is designed to look.
For example: If you have 9 different designs for the letter ‘a’, you have 9 glyphs.
A collection of glyphs in the same design family is considered a typeface. A collection of organised glyphs can be used to spell words.