Some meditation teachers feel that the following information should not be made available to the general public. That isn't because these teachings are for members of a select group, must be specially transmitted, or are in any sense esoteric; but because, due to the tricky nature of the mind, learning about these insights before acquiring personal meditation experience might cause you to anticipate results, thereby slowing your progress. That's why Mahási Sayádaw wrote, "It is not good for a pupil who meditates under the guidance of a teacher to get acquainted with these stages before meditation begins" (Practical Insight Meditation, p. 35).
Nevertheless, the Sayadaw agreed to the publication of his own book, The Progress of Insight, that deals with these stages. He acknowledged that the information may be helpful for many students who practice in isolation. So we decided to follow a middle path by publishing the present essay, but including a cautionary note as the Sayadaw did.
Generally speaking, we do not recommend that beginners read this article. We offer the following descriptions for those students who have no access to an instructor and are trying to make sense of a meditation experience they have had, or for those who have already reached a fairly advanced stage of insight.
Although it is natural to want to know what level you have reached and what will happen next in meditation, it is quite difficult to evaluate your own experience, even with a written guideline. You should always be aware that, no matter what you come to believe as a result of reading this article, your self-assessment may be incorrect. Besides, the mind likes to play tricks. If you cling to something you've read about, wanting it to happen, the mind may subconsciously try to mimic the experience. Without a teacher you may not be able to tell the difference between the illusion and the real thing. In order to avoid the trap of self-deception it is important to use the information given here intelligently, with continuous self-examination and scrupulous honesty.
If you are reading this because you are wondering if you have reached enlightenment, please realize that you probably haven't, although you may have reached an earlier stage of insight-knowledge. Achan Sopako Bodhi explains that when the first level of enlightenment is reached there can be no doubt about it. You would not need to ask if you'd attained it. In the words of another bhikkhu, "It cannot be missed."
That was from http://www.vipassanadhura.com/sixteen.html#toc
Okay, that said...
Of the traditional sixteen stages of Vipassana Knowledge before the first dip in nibanna, bhanga is number five.
1 Knowledge to distinguish mental and physical states (namarupa pariccheda nana).
2 Knowledge of the cause-and-effect relationship between mental and physical states (paccaya pariggaha nana).
3 Knowledge of mental and physical processes as impermanent, unsatisfactory and nonself (sammasana nana).
4 Knowledge of arising and passing away (udayabbaya nana). 5 Knowledge of the dissolution of formations (bhanga nana).
6 Knowledge of the fearful nature of mental and physical states (bhaya nana).
7 Knowledge of mental and physical states as unsatisfactory (adinava nana).
8 Knowledge of disenchantment (nibbida nana).
9 Knowledge of the desire to abandon the worldly state (muncitukamayata nana).
10 Knowledge which investigates the path to deliverance and instills a decision to practice further (patisankha nana).
11 Knowledge which regards mental and physical states with equanimity (sankharupekha nana).
12 Knowledge which conforms to the Four Noble Truths (anuloma nana).
13 Knowledge of deliverance from the worldly condition (gotrabhu nana).
14 Knowledge by which defilements are abandoned and are overcome by destruction (magga nana).
15 Knowledge which realizes the fruit of the path and has nibbana as object (phala nana).
16 Knowledge which reviews the defilements still remaining (paccavekkhana nana).
Then comes nibanna.
Here's a simple (simplistic?) description of what bhanga is like.http://www.vipassanadhura.com/sixteen.html#fourb
As for what nibanna is like... um... nah, I have no idea. The unconditioned? I think it's the ultimate indescribable thing.
But it's really different from bhanga. Some people think they have encountered nibanna when really they have just had some new and interesting experience of one of the other stages.
One word of caution, don't read through the Stages of Insight list and try to work out what stage you are at. It's so so easy to mis-read and get all mixed up. "Scripting" is a danger too.
Have you just finished a Goenka Vipassana course or something?