Daniel M. Ingram:
The Vipassana Jhanas are another map of the territory of stages of insight that adds in some of the useful information from the samatha jhanas. I write about them here MCTB The Vipassana Jhanas. There are some discrepancies between how various authors line up some aspects of the insight stages and vipassana jhanas, which I cover in MCTB, but this model presented here is the one typically used on this site, just to standardize terminology.
Really, one could say that the basic strata of mind being talked about are the jhanas in their basic or raw form, the natural jhanas as Kenneth Folk calls them, and one can look at them with different focuses to see them as samatha or vipassana jhanas. From another point of view, there are some distinct differences, though these may blur significantly, particularly at high levels of concentration and with different techniques.
In that vein, there are models that involve sub-aspects of the vipassana jhanas, called vipassana sub-jhanas, and then there are sub-sub-jhanas within those, leading to some very complex though sometimes useful models.
The First Vipassana Jhana is about effort to stay with objects, about concentration made strong by effort, and about some bodily bliss and joy, thought not as strong as in the next jhana. It encompasses the following insight stages: Mind and Body, Cause and Effect, and The Three Characteristics. However, as we will see, these stages, particularly The Three Characteristics, is typically not anything resembling pleasant, leading to the first of the tensions between the samatha jhanas and their vipassana counterparts. Attention is narrow, even if a wide focus is attempted, and effort is predominant.
The Second Vipassana Jhana arises when most of the effort drops away through practice becoming more natural by whatever cause, and the rapture and bliss can really predominate. It comprises the stage of the Arising and Passing Away (A&P). Attention is slightly wider and practice is natural or may even seem to overpower us.
The Third Vipassana Jhana arises when the second jhana sort of inverts itself, and in general the third aspect of these things, particularly in the sub-jhana models, tends to imply an inversion, a difficulty, a hard aspect to the thing. Whereas the second jhana has straight-on attention with the center being clear, in the third vipassana jhana the center is out of phase in some way with what attention is turned to, with the periphery being the clear part, which is very unintuitive for most people, so this phase can cause difficulties for those who are not looking for this and even for those who are. This vipassana jhana encompassas the Dark Night, aka Knowledges of Suffering, aka the Dukkha Ñanas, namely Dissolution, Fear, Misery, Disgust, Desire for Deliverance, and Re-Observation. As the old texts say, "Happy is he who has mindfulness and equanimity" in the third jhana, implying correctly that those who do not will not be happy, as is commonly seen.
The Fourth Vipassana Jhana is panoramic, related to Equanimity, both the quality and the insight stage, and also encompasses the stages of Conformity, Change of Lineage, and Path. It is broad, generally more neutral in feel than the previous two, and often, thought not always less intense.