Kowtow, which is borrowed from koutou in Mandarin Chinese, is a tranditional prostration common in Eastern Asia. Kowtow means kneeling and knocking one's head onto the ground. Kowtow is used in showing respect to parents or godnesses, or as a form of punishment by the parents when one has done something wrong. In the Qing Dynasty of China, the main usage of kowtow was to show respect and loyalty to the king.
Nowadays, people seldom kowtow and bow to others instead. However, in some Chinese weddings, the couple kowtow to the parents. At some schools in Taiwan, students still have to kowtow to thank their teachers.