Originally posted by Seig
Sorry I didn't answer sooner, didn't see your post. It's really very simple. There are three main form systems in TKD. The chung-ji forms( I know that in english there are different ways to spell these), the first form in this system is Ki-Cho. Then you have Tae-geuk(aka the hidden forms) which some describe as an extension of the Chung-ji forms. This is not necessarily true, there are subtle differences, such as the stances being shorter. Then there are the Pal-Gae forms, they were developed in what is now North Korea and do not have wide spread useage. Those forms are still very similiar but the stances are even closer(shorter) yet.
It's basically like syaing I have ranks in ITF vs WTF or the different Kwans.