In European and West Asian typography, the baseline is the line upon which most letters “sit” and below which descender extend. Check out the image below.
Most, though not all, typefaces are similar in the following ways as regards the baseline:
– capital letters sit on the baseline. The most common exceptions are the J and Q.
– Lining figures (see Arabic numerals) sit on the baseline.
East Asian scripts have no baseline; each glyph sits in a square box, with neither ascenders, nor descenders. When mixed with scripts with a low baseline, East Asian characters should be set so that the bottom of the character is between the baseline and the descender height.