Bunkai Jutsu posts What's The Difference Between Karate & Tae Kwon Do? Huh? Are they different?
Tae Kwon Do (or Taekwondo, or Taekwon-do) is a relatively new style.
There are those who claim a lineage of ancient arts in Korea, but, the essence of the martial art (which is not really a single art, but a collection of styles), is, as the author states, based on Shotokan.
Now, this gets really confusing, because, as some of my fellow MA bloggers have noted, there's a diversity of thought and expression of TKD throughout the USA, and the world. But as to it's origins, he's right.
The thrust (yes, I meant that) of the post is on the differences, and he does a fine job on that count. Read more, and yell at me in the comments.