What it means
Line height helps determine how a paragraph feels and how easily the eye finds the next line. Font size alone cannot tell you the ideal value: x-height, line length and the density of the letterforms also matter. A short display heading and a long paragraph usually need different treatment.
Use it in practice
Adjust line height while reading a real paragraph. Test at narrow widths where line wrapping changes the pattern.
Watch out for
Too little space can merge lines visually; too much can make a paragraph feel disconnected. Keep headings and their supporting text visibly related.
