Ask me again if someone want the reference links.
Follow ven. Pa-Auk for going in detail.
- sīlavisuddhi
Purification of personal behavior, verbal/physical. It's physical wholesome.
- cittavisuddhi
Purification of mind moment's behavior, mental. It's mental wholesome.
- diṭṭhivisuddhi
Purification of view about above body's elements and mental elements. The opposite view is mole-view, never analysis as elements completely perfectly.
- kaṅkhāvitaraṇavisuddhi
Purification of view about the sequential process of body's elements and mental elements in the sequence of the dependent origination. The opposite view is the mole-view which become into the doubt about the sequential process of body's elements and mental elements (kaṅkhā).
So, if the practitioner has wrong idea about body's elements and mental elements because of no diṭṭhivisuddhi, the practitioner will mistakenly relate the relation of body's elements and mental elements. Then this step will go wrong.
Seeing the dependent origination should switching with recalling-pastlife-skill like the Buddha did at his enlightening night because only past life's karma and unwholesome of rebirth moment are easiest to see "do good get good, do bad get bad". This moment has only one karma effecting, which appear at the last mind-process of past life. The other moments are effected by wholesome and unwholesome, so the ordinary often mistakenly think "do good get bad, do bad get good".
After the Purification of view about the sequential process of body's elements and mental elements in the order of the dependent origination, then the practitioner can see mind's moment, trillion times per second, arising and vanishing. This is the beginning of seeing three characteristic of the realities, body moment and mind moment.
In this step, the practitioner can analysis between real wholesome mind moment, real unwholesome mind moment, trillion times per second. If not, use kalapasammasana method to practice this step until proficiently seeing the realities' arising and vanishing sequentially and relatively, trillion times per second.
- maggāmaggañāṇadassanavisuddhi
Real wholesome mind moment is called Magga (path).
Real unwholesome mind moment is called Amagga (not path).
The object of above diṭṭhivisuddhi and kaṅkhāvitaraṇavisuddhi are three noble truth, except nibbana (cessation-noble-truth, because the practitioner can't see nibbana until enlightening moment arising).
Proficiency of understanding uncountable realities' arising and vanishing possibility of three noble truth is called ñāṇa (dukkhe ñāṇa, etc.)
Above ñāṇa is viewing uncountable realities' arising and vanishing possibility of three noble truth like a photographic memorial genius sciences seeing atomic structure in his head, so this ñāṇa is called dassana.
The above views, diṭṭhivisuddhi and kaṅkhāvitaraṇavisuddhi, are purified or not, are depending on how clear the practitioner seeing the noble truth. If the practitioner can't see the entire possible unwholesome arising on entire possible objects, Then this step will go wrong because the hidden unwholesome will arise between the insight meditation. And the unwholesome in this step is what the ordinaries never think they are unwholesome. That's one important of many reasons why we need to see the momentary arising and vanishing.
The practitioner can't see the momentary arising and vanishing without above proficient of kaṅkhāvitaraṇavisuddhi skill. The practitioner is going to be bias, dirty, confuse, complicated, misunderstood about analysis of real wholesome, real unwholesome, neither wholesome nor unwholesome. Then this step will go wrong.
That's why it's named maggāmaggañāṇadassanavisuddhi.
- paṭipadāñāṇadassanavisuddhi
Proficiency of keeping the insight meditation going on, without any unwholesome in between, by understanding uncountable realities' arising and vanishing possibility of three noble truth is called ñāṇa (dukkhe ñāṇa, etc.)
Above ñāṇa is viewing of keeping the insight meditation going on, without any unwholesome in between, by understanding uncountable realities' arising and vanishing possibility of three noble truth like a photographic memorial genius sciences seeing atomic structure in his head, so this ñāṇa is called dassana.
If above maggāmaggañāṇadassanavisuddhi has only one unwholesome moment inbetween. Then this step will go wrong. Restart the meditation from sīlavisuddhi again.
- ñāṇadassanavisuddhī
It's enlightening moment. All ñāṇa and dassana are purified at this only moment.