What is Baseline? - Typography Lexicon

The characters of typefaces sit on an imaginary line, which does not shift even when characters are enlarged or reduced in size. This line is called the baseline. The lower elements of characters such as y, g, q etc. dangle down to the descender and the upper elements of b, d, f etc. reach up to the ascender. On enlargement or reduction of the character size, only the ascenders and descenders shift but not the base line.