To answer Hope Rainbow's question, terms like "pure land", "paradise", "heaven" and "Buddhafield" are synonymous. "Merit field" can be defined as "the object of one's offering, devotion, etc., through which one can accumulate merit and wisdom. The term usually refers to refuge deities, one's guru in the guru yoga etc.
Pure lands are really fascinating. There are millions of them. Some books give their approximate locations, for example in the Amitabha Sutra, the Buddha said that the pure land of "Ultimate Bliss" (Sukhavati) is more than a hundred thousand million Buddha lands to the west of the saha world.
From my reading, I discovered that there are also different types of pure lands: the distinctive pure lands of the Mahayana School (eg. Sukhavati), the pure land of the Three Vehicles, the pure land of the Five Vehicles (eg. Tushita Pure Land) and the pure land on Earth.
The last heaven is really interesting because it is what we can aspire to immediately. It is said in the Vimalakirti Sutra, that although Vimalakirti lived in the saha world, his state of mind was that of the Pure Land. Both heaven and hell are in one's mind. As we are still in samsara at this moment, the way we can be close to the Buddha is to work to transform the saha world into a pure land on Earth. Once Sariputra asked the Buddha, "The Buddha lands of the ten directions are all very pure. Why is our saha world so corrupt and filthy?" The Buddha replied, " You cannot comprehend the world in which I live." With this, the Buddha pressed the earth with his toe. Immediately, the world became brilliant, pure and magnificent. The Buddha then continued, "This is the world in which I live."