A very concise explanation based upon various Sutta’s relating to Nibbana can be heard from Ven.Katukurunde Nanananda Thero who has given proper explanation on what is Nibbana and how should one understand it.
There are 33 sermons and a book of this one was also suggested by Lal in one of his posts. The only issue is with Anicca and Anatta explanation and other than that, it is a good place to understand on Nibbana.
In the Jatasutta of the Samyutta Nikāya, Buddha hints on Nibbana as under:
Yattha nāmañca rūpañca,
asesa uparujjhati,
patigham rūpasaññā ca,
etthesā chijjate jatā.
Where name and form
As well as resistance and the perception of form
Are completely cut off,
It is there that the tangle gets snapped.
This answer is given by Buddha to a certain deity which asked a question on tangle within a tangle
Anto jatā bahi jatā,
jatāya jaitā pajā,
tam tam Gotama pucchāmi,
ko imam vijataye jatam
“There is a tangle within, and a tangle without,
The world is entangled with a tangle.
About that, oh Gotama, I ask you,
Who can disentangle this tangle?”
So basically, Nibbana is a stage where avijja of maha-bhuta’s no longer exist and tanha for possessing them does not exist, there arises Nibbana. In that neither I or we or anything which can be explained through language or syntax exist.
Thus, rupa, chitta and chetasika are of this world and nibbana is not of this world since there is no existence of rupa-nama. Thus there is no designation, language and vocabulary as in nama and no possession of rupa.
In another way, adhivacanasamphassa and paighasamphassa no longer is in contact or phassa and thus nama-rupa does not meet up thus stopping the vortex of samsara. This is also called nibbana.
It would be good to read about Maha Nidānasutta which not only explains PS but also gives indepth explanation of each paccaya especially on namarupa paccaya vinnana and vinnana paccaya namarupa. In that also, you can see nibbana arising when namarupa and vinnana is cut off. Meaning, the craving for nama-rupa is completely eliminated thus stopping the need for existence.
This stopping of existence is called nibbana