In Jazz, Funk, Fusion, or Modern R&B, you will often find chords which extend past the 7th, notably various types of 9th, 11th and 13th chords. These higher numbers come about by repeating the scale from which they are derived over two octaves. Thus, in the higher octave the 2nd becomes the 9th, the 4th becomes the 11th and the 6th becomes the 13th, as shown here in the key of C.
As you have already learned, most chords are made up of various 3rd intervals stacked one on top of the other. This means that by going through a scale in thirds (i.e., skipping every second note) it is easy to create chords up to a 13th.
Depending on the nature of the degrees of the chord, 9ths 11ths and 13ths may be either major, minor or dominant in quality. E.g., if you add a 9th degree on top of a dominant 7th chord, you end up with a dominant 9th chord (usually just called a 9th chord). If you add a 9th degree on top of a minor 7th chord, you end up with a minor 9th chord, etc. The following example demonstrates the use of extended chords. If you wish to learn more about chords and their uses, see Progressive Complete Learn to Play Piano Manual, or Progressive Complete Learn to Play Jazz Guitar Manual.