There are three main traditional schools of Zen in Japan, each with its own background and specificities.
The Soto Sect
Soto is the largest of the sects. Historically practiced by the lower classes, artists, and poets, the Soto sect emphasizes the practice of sitting meditation known as zazen. Practitioners face a wall or a curtain during this meditation.
The Rinzai School
Traditionally practiced by the samurai caste, the Rinzai School include the presence of Koan, a kind of short and paradoxical sentence that cannot be solved intellectually. However, those are usually introduced only after good posture and concentration were achieved during the seated meditation.
The Obaku Sect
The smallest of the sects, the Obaku sect was formed by a small group made up of Buddhist masters from China and Japanese students at the Manpuku Temple (Manpuku-ji). To this day, those in the Obaku sect continue to chant sutras in the Chinese language.