The quick brown fox jumps over the lazy dog.
Typography is the art and technique of arranging type to make written language legible, readable, and appealing when displayed. The arrangement of type involves selecting typefaces, point sizes, line lengths, line-spacing (leading), and letter-spacing, as well as adjusting the space between pairs of letters.
Good typography requires an understanding of the relationship between font metrics and the space around the text. The ascender height, x-height, and descender depth all influence how dense a block of text appears, and therefore how much leading is needed to maintain comfortable reading rhythm.
Drop your own font file to see how its unique proportions affect the optimal line-height for your chosen font-size and measure.