What’s the practical difference between these two states?
And what does “extinguished” mean in this phrase: “All that is experienced, not being delighted in, will be extinguished”?
What’s the practical difference between these two states?
The short answer is that it is referring to the arahant before and after the breakup of their body. Here is Bhikkhu Bodhi’s notes from his SN translation with the most relevant part bolded:
As is well known, nibbāna literally means the extinction of a fire. In popular works on Buddhism, nibbāna plain and simple is often taken to signify Nibbāna as experienced in life, parinibbāna Nibbāna attained at death. This is a misinterpretation. Long ago E.J. Thomas pointed out (possibly on the basis of a suggestion by E. Kuhn) that the prefix pari- converts a verb from the expression of a state into the expression of the achievement of an action, so that the corresponding noun nibbāna becomes the state of release, parinibbāna the attaining of that state. [History of Buddhist Thought, p. 121, n. 4.] The distinction does not really work very well for the verb, as we find both parinibbāyati and nibbāyati used to designate the act of attaining release, but it appears to be fairly tenable in regard to the nouns. (In verse, however, we do sometimes find nibbāna used to denote the event, for example in the line pajjotass’ eva nibbānaṃ at v. 612c.) Words related to both nibbāna and parinibbāna designate both the attaining of release during life through the experience of full enlightenment, and the attaining of final release from conditioned existence through the breakup of the physical body of death. Thus, for instance, the verb parinibbāyati is commonly used to describe how a bhikkhu achieves release while alive (e.g., at II 82,20; III 54,3; IV 23,8–9, etc.) and also to indicate the passing away of the Buddha or an arahant (e.g., at I 158,23; V 161,25).
The past participle forms, nibbuta and parinibbuta, are from a different verbal root than the nouns nibbāna and parinibbāna. The former is from nir + vṛ, the latter from nir + vā. The noun appropriate to the participles is nibbuti, which occasionally occurs in the texts as a synonym for nibbāna but with a function that is more evocative (of tranquillity, complete rest, utter peace) than systematic. (It seems no prefixed noun parinibbuti is attested to in Pāli.) At an early time the two verb forms were conflated, so that the participle parinibbuta became the standard adjective used to denote one who has undergone parinibbāna. Like the verb, the participle is used in apposition to both the living Buddha or arahant (I 1,21, 187,8) and the deceased one (I 122,13, 158,24). Possibly, however, parinibbuta is used in relation to the living arahant only in verse, while in prose its technical use is confined to one who has expired. In sutta usage, even when the noun parinibbāna denotes the passing away of an arahant (particularly of the Buddha), it does not mean “Nibbāna after death.” It is, rather, the event of passing away undergone by one who has already attained Nibbāna during life.
The suttas distinguish between two elements of Nibbāna: the Nibbāna element with residue (sa-upādisesa-nibbānadhātu) and the Nibbāna element without residue (anupādisesanibbānadhātu )—the residue (upādisesa) being the compound of the five aggregates produced by prior craving and kamma (It 38–39). The former is the extinction of lust, hatred, and delusion attained by the arahant while alive; the latter is the remainderless cessation of all conditioned existence that occurs with the arahant’s death. In the commentaries the two elements of Nibbāna are respectively called kilesaparinibbāna, the quenching of defilements at the attainment of arahantship, and khandhaparinibbāna , the quenching of the continuum of aggregates with the arahant’s demise. Though the commentaries treat the two Nibbāna elements and the two kinds of parinibbāna as interchangeable and synonymous, in sutta usage it may be preferable to see the two kinds of parinibbāna as the events which give access to the two corresponding Nibbāna elements. Parinibbāna, then, is the act of quenching; nibbāna, the state of quenchedness.
To explain the philology of a term is not to settle the question of its interpretation. What exactly is to be made of the various explanations of Nibbāna given in the Nikāyas has been a subject of debate since the early days of Buddhism, with the ground divided between those who regard it as the mere extinction of defilements and cessation of existence and those who understand it as a transcendental (lokuttara) ontological reality. In SN some suttas explain Nibbāna as the destruction of lust, hatred, and delusion, which emphasizes the experiential psychological dimension; elsewhere it is called the unconditioned, which seems to place the stress on ontological transcendence. The Theravāda commentators regard Nibbāna as an unconditioned element. [This is clearly maintained in the debate on Nibbāna recorded at Vism 507–9 (Ppn 16:67–74). See too the long extract from the Paramatthamañjūsā, Dhammapāla’s commentary on Vism, translated by Ñāṇamoli at Ppn pp. 825–26, n. 18.] They hold that when Nibbāna is called the destruction of the defilements (of lust, hatred, and delusion, etc.) and the cessation of the five aggregates, this requires interpretation. Nibbāna itself, as an existent, is unborn, unmade, unbecome, unconditioned (see Ud 80–81). It is in dependence on this element (taṃ āgamma), by arriving at it, that there takes place the destruction of the defilements and release from conditioned existence. Nibbāna itself, however, is not reducible to these two events, which are, in their actual occurrence, conditioned events happening in time. On this interpretation, the two Nibbāna elements are seen as stages in the full actualization of the unconditioned Nibbāna, not simply as two discrete events.
In the present work I leave nibbāna untranslated, for the term is too rich in evocative meaning and too defiant of conceptual specification to be satisfactorily captured by any proposed English equivalent. I translate parinibbāna as “final Nibbāna,” since the noun form usually means the passing away of an arahant (or the Buddha), final release from conditioned existence; sometimes, however, its meaning is ambiguous, as in the statement “the Dhamma [is] taught by the Blessed One for the sake of final Nibbāna without clinging (anupādāparinibbānatthaṃ)” (IV 48,78), which can mean either Nibbāna during life or the full cessation of existence.
The verb parinibbāyati perhaps could have been incorporated into English with “nibbanize,” which would be truest to the Pāli, but this would be too much at variance with current conventions. Thus when the verb refers to the demise of the Buddha or an arahant, I render it “attains final Nibbāna,” but when it designates the extinguishing of defilements by one who attains enlightenment, I render it simply “attains Nibbāna.” We also find a personal noun form, parinibbāyī, which I render “an attainer of Nibbāna,” as it can be construed in either sense. In prose the past participle parinibbuta, used as a doctrinal term, always occurs with reference to a deceased arahant and so it is translated “has attained final Nibbāna.” In verse, it can take on either meaning; when it describes a living arahant (or the Buddha) I translate it more freely as “fully quenched.” The unprefixed form nibbuta does not always carry the same technical implications as parinibbuta, but can mean simply “peaceful, satisfied, at ease,” without necessarily establishing that the one so described has attained Nibbāna. [For a play on the two senses of nibbuta, see the Bodhisatta’s reflections before his great renunciation at Ja I 60–61.] At I 24,11 and II 279,8 it has this implication; at I 236,21 it seems to mean simply peaceful; at III 43, in the compound tadaṅganibbuta, it definitely does not imply Nibbāna, for the point there is that the monk has only approximated to the real attainment of the goal. Cognates of parinibbāna appear in colloquial speech with a nondoctrinal sense; for example, both parinibbāyati and parinibbuta are used to describe the taming of a horse (at MN I 446,8–10). But even here they seem to be used with a “loaded meaning,” since the horse simile is introduced to draw a comparison with a monk who attains arahantship.