TYPOGRAPHIC BASELINE IN A NUTSHELL
As part of typesetting or typography, baseline is the line that most of the letters sit on the line. Specifically, in terms of the western alphabet most capital letters will sit on the baseline with minor exceptions. Letters like j or y have descenders that go below the baseline to complete the letter. Letters like n sit on the baseline and extend up to the median. Some letters like O, Q, or c do not sit exactly on the baseline but extend below by a small amount but the overall effect is that they sit at the same height as noncurved letters.