TKD is a very exciting martial art that is designed for self-defense.  There are many directions to go with this art.  You can practice the traditional art by learning the forms and techniques.  There is also the sport aspect of Tae Kwon Do that got it selected as an Olympic sport.  The sport style is much more dynamic with faster kicks and more fluid stances.  Many schools teach both and some focus solely on one of these styles.

A brief history of Tae Kwon Do

Early Koreans developed unique martial art forms for unarmed self defense to complement their skills with weapons. The first recorded evidence of what was to become modern Tae Kwon Do is found about two thousand years ago in Korean history. A mural painting from the Koguryu kingdom (37 B.C to 66 A.D.) was found in a tomb believed to have been built sometime during the period 3 to 427 A.D . This mural depicts figures practicing martial arts techniques. Historical records from this Koguryu period also mention the practice of martial arts techniques and tournaments. The early forms had different names, such as Kwonbak, Bakhi, Dangsoo, Taesoo and Kongsoo. From about 600 A.D. to about 1400, the main stream dominant form was Soobak, which further evolved into Taekyon beginning in the late 1300s. Taekyon was the dominant Korean martial art form until the Japanese invasion and occupation of Korea in 1909. From 1909 to 1945, the Japanese suppressed Korean culture and martial arts, and introduced Japanese culture and martial arts.

The modern period of Taekwondo began with the defeat of the Japanese and the liberation of Korea in 1945. Korean martial arts masters wanted to eliminate Japanese influences. They began discussions on how to return to the traditional Taekyon based Korean martial arts and on how to unite the various martial arts schools (or Kwans) and styles into a single style and national sport. After several years of discussions, the name "Taekwondo" was chosen in April 1955 by the board of masters of the various Kwans, and the kwans started to unify through the late 1950s.

http://www.tkd.net/tkdnetwork/history.html

An ancient Korean monk by the name of Won Kwang Bupsa authored the now famous Sesokokye, the following five commandments.

• BE LOYAL TO YOUR COUNTRY.
• HONOR YOUR PARENTS.
• BE FAITHFUL TO YOUR FRIENDS.
• NEVER RETREAT IN BATTLE.
• USE GOOD JUDGMENT BEFORE KILLING LIVING THINGS.

These commandments became a basic way of life, giving values and principles for living to those involved in Tae Kwon Do training.