The document discusses factors that affect the readability and legibility of type, including type size, leading, kerning, line length, font selection, and typeface selection. It notes that the upper halves of characters are easiest for the eye to scan, making lowercase text more readable than uppercase. The spacing between letters, words, and lines should not be too tight or too loose, as either can disrupt readability. Line length should generally not exceed 35-70 characters to aid readability.