Jhana is a Pali word meaning "absorption." The corresponding Sanskrit word is dhyana. The Chinese word Chan and the Japanese word ''Zen'' are both derived from jhana or dhyana. When we speak of jhana, we are referring to a state of profound concentration that results from focusing the mind on some mental or physical phenomenon. Traditional objects of meditation include the the breath, fixing the mind on a mental image or sound, or gazing at a colored disk (''kasina''), among many others.
It is useful to differentiate between samatha (Sanskrit shamata) jhana and ''vipasssana'' jhana. In the case of samatha jhana, the goal of the meditator is to enter and abide in various discrete states of profound concentration. There is no effort to investigate the true nature of the experience; rather, the exquisitely concentrated state itself is the goal of the exercise. Samatha jhana has the effect of suppressing negative mind states ("hindrances") both during and for some time after the experience, so it is also seen as a support for vipassana meditation.
Vipassana jhana, depending on the speaker, can refer to either a state or a stage of meditation. As a state, a vipassana jhana corresponds directly to a similarly named samatha jhana, but with one important difference: in vipassana jhana, the point is not simply to abide in a pleasant state, but to penetrate to the true nature of the experience by carefully investigating the three characteristics of that experience. Jhanas, therefore, can be viewed as discrete strata of mind that can be accessed by either the samatha or vipassana technique. A skilled meditator can visit the various strata of mind at will, in any order, and either become absorbed in the jhana using pure samatha or investigate it via vipassana.
When the phrase "vipassana jhana" is used to describe developmental stages of meditation rather than discrete states of mind, it refers to the territory that includes and brackets the corresponding samatha jhana. In other words, the 1st vipassana jhana is larger than the 1st samatha jhana and includes the 1st, 2nd, and 3rd ''ñanas'', or insight knowledges. Because a meditator develops through the Progress of Insight in a predictable way, from beginning to end, it is possible to describe an individual's progress by talking about vipassana jhanas. One might say, for example, that a yogi has passed through the 1st vipassana jhana, a process which might have taken days or weeks or years, depending on the individual, and is now working on the 2nd vipassana jhana. When speaking of jhana (the generic term for calmly abiding) and jhanas (discrete states or specific stages of development), it is good to be clear about which sense of the word is intended.
The traditional list of four rupa (material) and four arupa (immaterial) jhanas is derived from the original Theravada texts and tradition, and is a very good and accurate description of the standard, natural states that one progresses through when learning to concentrate and get into the meditative states that concentration leads to.
The first four states are known by their numbers, and thus are:
These are followed by jhanas not explicitly mentioned in the Theravada Texts but occur anyway, namely what we at the Dharma Overground community refer to as the Pureland Jhanas:
The Pureland jhanas are vipassana/samatha hybrids, and are only available to those advanced practitioners who have attained to the level of anagami or arahat. As such, they are useful landmarks of progress; a person who can access either of the Pureland jhanas is, by definition, at least an anagami. Traditionally, these states are referred to as part of the suddhavasa or "pure abodes."
There is also an attainment that is related to these but is not quite a concentration state called Nirodha Samapatti aka The Cessation of Perception and Feeling, sometimes simply referred to as Nirodha, though Nirodha may also mean Fruition, so when speaking of these phenomena it is useful to specify which meaning is intended. Like the Pureland jhanas, Nirodha Samapatti is only available to those who have attained to at least the level of anagami.
There are multiple axes on which jhanas may develop, see Jhana Development Axes.