Watch the The Dominant 9th Chord online guitar lesson by Frank Vignola from 1-2-3 Jazz Guitar
The 3rd chord is the dominant 9th chord. Place your 2nd finger on the C at the 3rd fret of the 5th string, your 1st finger on the 2nd fret of the 4th string, your 3rd finger is placed on the 3rd fret of the 3rd string and creates a "bar" to fret the top 3 strings. Note that we use the flesh of the second finger to dampen the 6th string since we are not using the low E string. This is another moveable chord, but in this case the root of the chord is found on the 5th string. Therefore this is a C dominant 9th chord because the 3rd fret of the 5th string is a C. You can move this shape up and down the fingerboard and the note your 2nd finger is playing on the 5th string is the name of the chord.