Definitions for "Advance Width"
Keywords:  glyph, width, 'hmtx, 'hdmx, ppem
The distance between the start of this character and the start of the next character. Sometimes called the character's width.
The full horizontal width of a glyph as measured from its origin to the origin of the next glyph on the line, including the side bearings on both sides.
The ''advance width'' of a glyph is the movement in the direction of writing from the starting point for rendering that glyph to the starting point for rendering the next glyph.