Taekwondo has been an Olympic sport since the year 2000. Athletes wear a white uniform called a dobok and a coloured belt to show their level - starting with white (beginner), then yellow, green, blue and red, all the way up to black (expert). It can take years of training to earn a black belt.
The most famous taekwondo moves are kicks. Top fighters can spin in mid-air and kick a target two metres off the ground - higher than their own head. Practising those kicks takes balance, flexibility and a lot of stretching, because the legs need to be able to reach high without getting hurt.
Lessons usually start with a bow to your teacher and your training partner. After that, students warm up, practise patterns of moves called poomsae, and then practise sparring (controlled, padded mock-fights). The bow at the beginning and the end is a sign of respect - taekwondo treats everyone in the room as a partner, not an enemy.
Around 80 million people practise taekwondo around the world. It is taught in schools in over 200 countries. The headquarters of world taekwondo, called Kukkiwon, is in Seoul, and teams from every continent travel there to take their black-belt tests.