The 9th chords are based on the: 1st (Root) - 3rd - 5th - 7th & 9th(2) notes of a major scale.
It is common to play a voicing (only 3 or 4 of the notes) of the 5 notes of the chord. This provides for a more open sound and if you play with a Bass guitar it is also common to exclude the Root of the chord since the Bassist will play it. These chord symbols are common to other instruments such as keyboards.
There are many variations of these voicings as such the more common ones are presented here. Inversions are also played using voicings and will be noted by the chord symbol. To explore more possibilities try including the use of alterations such as adding a #5, b5, #9, etc.,. All of these patterns are block forms and moveable.
