A is a unique form of Japanese chair

Chair

A chair is a stable, raised surface used to sit on, commonly for use by one person. Chairs are most often supported by four legs and have a back; however, a chair can have three legs or could have a different shape depending on the criteria of the chair specifications. A chair without a back or...

 which has no legs, but has a normal chair back. Traditionally, the Japanese would sit in or 'correct' sitting style, kneeling with their weight on top of their lower leg, which is folded underneath the body. However this can become painful after long periods of time or for people who are not used to it, so many prefer the more comfortable zaisu option where the back is supported and legs can be sprawled in front.

Zaisu are very common in Japan, particularly in houses that have traditional Japanese style rooms where low tables and sitting on a floor of tatami mats

Tatami

A is a type of mat used as a flooring material in traditional Japanese-style rooms. Traditionally made of rice straw to form the core , with a covering of woven soft rush straw, tatami are made in standard sizes, with the length exactly twice the width...

are commonplace.