C2 B13 and Ab7(b9) ?

[Kalis Reign]

I keep encountering chords like these in the tableture I find. Is there like a lesson or something which helps you learn how to construct chords like G9(13) or C2?

[The Fury]

Yep, try this: http://www.cyberfret.com/classic/how_chords_work.htm

It will help to have a basic understanding of the major scale.

There are some more lessons here: http://www.cyberfret.com/classic/index.htm

I hope this helps.