Jodo (Pure Land) (浄土)
Edo (Impure land)
The Edo, as opposed to Jodo, is also called Ekoku (defiled land), a land filled with Eaku (impurities).
The Bukkokuhon (the chapter of Buddha-land) "Yuimagyo (Vimalakirti Sutra)" describes that 'there are hillside, mine-pit halls, thorns, a million stones, earth and sand, many mountains and all filled with impurities.'
It describes lands, such as desert and undeveloped wastelands, as Ekoku.
The volume of "Muryoju-kyo Ubadaisha Ganshoge-chu" (Commentary on [Vasubandhu's] Upadesa on the Sutra of Immeasurable Life) says 'When you see three existences (past, present and future) of Edo, there is the dimension of the fallacious, the dimension of rotation and the dimension of infinitude, like an inchworm that circles or like a silkworm which ties itself in a cocoon.'
It means that Edo is the world of the fallacious, protean, where people circle around a ring like an inchworm does, and suffer by tying themselves up like a silkworm does within their cocoon.
In this place, the human beings have tied themselves up, looking at delusions without knowing they are delusional. They are obsessed with, and suffered from, these delusions, and this is the world of Bonno (earthly desires).
As opposed to Edo, where people can not feel any material and spiritual well being, Jodo (Pure Land) is a pure clean land. This sort of pure land is the legitimate land of Buddha. Hence, Jodo is the Buddha-land.
"Yuimagyo" says 'following that spirit being pure, hence the land of Buddha is pure', and "Shinjikan-gyo Sutra" also describes that 'Because the spirit is pure, the world becomes pure and because the spirit is impure, the world becomes impure.'
As seen from this, the pureness of the world depends on spirituality. Thus, the purity or impurity of the land is dictated by the spirit of the residents who live there.
Hence, the legitimate Jodo is the place Buddha resides, and the land of Bosatsu (Bodhisattva) who is devoted to becoming a Buddha. From this point of view, Jodo is the land of Buddha. However, although Jodo is the land of Buddha, the land of Buddha is not necessarily Jodo. The world for Buddha's edificatory purpose is also the land of Buddha, hence, the world of Bonpu (ordinary unenlightened person) could be the land of Buddha. This means the lands of Buddha indicate the adobe of Buddha and all edificatory worlds. Hence, the Jodo is the world of Bosatsu attaining to become a Buddha.
There are various traditions devoted to various Jodo. Amongst them, the Amida Buddha's "Seiho Gokuraku Jodo (The West Pure Land)" is a famous one. However, Ashuku-butsu's (Aksobhya Buddha) "Toho Myoki Sekai (the Eastern world of Delight)", Yakushi-butsu's "Toho Joruri Sekai (Eastern Pure Land)" and Shakamuni-butsu's "Musho Shogonkoku" are also well known. In that sense, the word 'jodo' (pure land) is a common noun rather than a proper noun.
If you ask what Jodo exists for, it is for Buddha himself to obtain the Horaku (pleasure of a pious life) as well as to lead people to this land and provide the Buddhist benefits in order for them to be spiritually awakened. The world of the impure hinders the ascetic in training from becoming a Buddha. That is why each Buddha leads one to Jodo and provides these Buddhist benefits in order to make it easier to do ascetic training. In this sense, the Jodo is a place for Buddha's satisfaction, and for the benefit of others - the satisfaction for both parties.
These Jodo are not in this world that we live in, but built in another world. People only go there when their life ends in this world, hence, the concept of Ojo Jodo (Birth in the Pure Land) exists. Significantly, the Amida-Buddha's Seiho Gokuraku Jodo forms the Jodo sect which takes the position of the Ojo Jodo.
There is another school of thought that, rather than teaching about the building of Jodo in another world, teaches that the world will shift to Jodo as is. More specifically, "Yuimagyo" states that if the spirit is pure then even soil is pure, and even in this world there could be the soil of pureness. For example, "Hokkekyo (Lotus sutra)" preaches to alter this corrupt world to the land of lapis lazuli of the Jodo world (Shabasoku jakko). This concept was taken by the Ryozen Jodo of Shaka (Shkyamuni) and the Lotus Matrix World of Birushana-butsu (Vairocana).
Places worshipped, like the Buddha-land, includes the inner temple of Tosotsuten (The fourth of six heavens in the world of desire) of Miroku Bosatsu (Buddha of the Future, Bodhisattva of the Present), and the Hodarakusen (Potalaka) of Kannon Bosatsu (Kannon Bodhisattva). In a certain sense, these places conform to Jodo.
The predominant feature of Jodo is the concept that besides the existence of Jodo in this world, Jodo was built by Buddha. To go to that Jodo, and attain enlightenment through being led by Buddha, is the belief of Jodo.