It’ll be a bit of long story, so grab some popcorn and get cozy!
Buddhism in general is named for the historical figure who came to our world as Siddhartha Gautama (also named ‘Shakyamuni’ for his clan of origin, the Shakya) and, after He attained enlightenment underneath a tree, became known as ‘The Buddha’ meaning ‘He who has been awakened’.
In Buddhism, it’s taught that this Buddha was not the only Buddha; He taught us what He had discovered. Indeed, all living thing have ‘Buddha nature’, the potential to attain that enlightenment and escape the cycle of birth, life, death, and rebirth through following the Buddha’s Teachings.
One of the later followers of the Dharma, named Dharmakara, began to study under a Bodhisattva named Lokeshvaraja. While under Lokeshvaraja’s tutelage, Dharmakara engaged in all kinds of varying Buddhist practices and had successfully attained enlightenment after trillions of years, becoming known by the more familiar name Amitabha Buddha (‘The Buddha of Infinite Light and Infinite Life’). Finding these practices extremely difficult especially for ordinary people, Amitabha decided to offer a much easier pathway to enlightenment through the creation of a place called a ‘Pure Land’. Pure Lands are free from defilement and evil, and lie far outside of the Six Realms of samsara (that cycle of birth, life, death, and rebirth spoken of earlier). There are countless of these. Amitabha had taught of 48 Vows dedicated to this much easier pathway, the 18th of which is called the Primal Vow. This 18th Vow basically says that any person who has sincere faith in Amitabha who aspires to be reborn into His Pure Land and recites His Name even ten times will be able to after death. The sincere understanding of this is what gives the school of Buddhism I adhere to its name: Pure Land Buddhism.
From India, it spread to China, and from China, to Japan. The first teacher there was named Genshin, and the second teacher of Japanese Pure Land was named Honen. Honen first studied at Mt. Hiei as a student of a school of Buddhism called ‘Tendai’. Influenced by Chinese Master Shandao, he became exclusively devoted to the chanting of Amitabha’s name (nianfo, in Japanese nembutsu). Honen established the Pure Land teachings in Japan under the name Jodo-shu (‘Pure Land’). His teachings, centered around the belief that we live in an age of Dharma decline (‘Mappo’), were simple and became wildly popular among average, everyday people. All kinds of people embraced his teachings!
During his life and after his death, his followers were exiled and spread out. Because of this, there developed different sects of the Japanese Pure Land teachings. One of his disciples, named Shinran, taught that our assurance of rebirth in the Pure Land was settled in this life, through Amitabha’s limitless compassion, the Other-Power. We didn’t have to wait until death for this! There were various other differences between Jodo-shu and Shinran’s teachings, which he called ‘Jodo Shinshu’ (‘The True Pure Land school’). Jodo Shinshu, like Jodo-shu, spread like wildfire in Japan, both becoming the two most popular sects of Buddhism there.