legibility has 3 questions, while readability has 24. They appear to be covering the same topics, and "readability" is something that I have heard more often in terms of how easy it is to read and understand code (also evidenced by the usage here, being 8 times more common).
Legibility != readability
From wikipedia (empasis mine):
Legibility is the degree to which glyphs (individual characters) in text are understandable or recognizable based on appearance.
Legibility is different from readability which refers to entire words, sentences, and paragraphs.
update: but as Mark notes, a tag wiki may not be the best thing for a tag without questions.