the C Major chord
As described in the lesson "Intervals and chords", a chord comprised of three notes is known as a triad. A triad that has 4 intervals between the 1st and 2nd notes (AKA a Major 3rd), and 3 intervals between the 2nd and 3rd notes (a minor 3rd) is known as a Major triad. Thus, the C Major chord is C-E-G.
And, from the lesson "Playing intervals and chords from the C position", you can view this triad as the two two-note chords C-E and E-G combined. Thus there is a white key in between playing fingers.