No, not the key signature. It is just an explanation of how the modes are formed, i.e. what the intervals between the notes are for each mode, since only the white keys are used.

So:

C Ionian (major)= C D E F G A B C
(you already know that this key shares its notes with it's relative minor key--A minor (A is 3 places to the left of C on the circle of fifths))

C Myxolydian (major with flatted 7th) = C D E F G A Bb C
(notice that this key has the same notes in its scale as the key 1 place to the left on the circle of fifths--the key of F major/also D minor)

C Aeolian (natural minor)= C D Eb F G Ab Bb C
(notice that this key (Cm) has the same notes as its relative major key, 4 places to the right on the circle---the key of E major)

C Dorian (minor with sharped 6th) = C D Eb F G A Bb C
(notice that this key shares it's notes with the one 3 places to the left on the circle--Bb major/ also G minor)

C Phrygian (minor with flatted 2nd) = C Db Eb F G Ab Bb C
(notice that this key shares it's notes with the one 4 places to the left on the circle--Ab major/also F minor)

C Pentatonic = C D E G A

C Pentatonic Minor = C Eb F G Bb C


Sorry, I screwed up above. The Pentatonic scale leaves out the 4th, not the 3rd, from the regular major scale. Hence, there IS a major/minor feel to it. The third in the C scale is E. When it's flatted to Eb, the chord is minor.