There are four stages of enlightenment (as described in the Anapanasati Sutta), Sotapanna, Sakadagami, Anagami and Arahant; stream-enterer, once-returner, non-returner and Arahant; respectively.
Stream enterer: A stream-enterer reaches arahantship within seven rebirths upon opening the eye of the Dharma.
...with the wasting away of [the first] three fetters, are stream-winners, steadfast, never again destined for states of woe, headed for self-awakening...
Once-returner: Both the stream-enterer and the once-returner have abandoned the first three fetters. The stream-enterer and once-returner are distinguished by the fact that the once-returner has weakened lust, hate, and delusion to a greater degree.
...with the wasting away of [the first] three fetters, and with the attenuation of passion, aversion, & delusion, are once-returners, who — on returning only once more to this world — will make an ending to stress...
Non-returner: The non-returner, having overcome sensuality, does not return to the human world, or any unfortunate world lower than that, after death.
...with the wasting away of the five lower fetters, are due to be reborn [in the Pure Abodes], there to be totally unbound, destined never again to return from that world...
Arahant: The fourth stage is that of Arahant, a fully awakened person. He has abandoned all ten fetters and, upon death will never be reborn in any plane or world, having wholly escaped saṃsāra.
...who are arahants, whose mental effluents are ended, who have reached fulfillment, done the task, laid down the burden, attained the true goal, laid to waste the fetter of becoming, and who are released through right gnosis...
Individuals may experience nirvāna as an object of mental consciousness. Certain contemplations with nibbana as an object of samādhi lead to the level of non-returning. At that point of contemplation if the individual realizes that even that state is constructed and therefore impermanent, the fetters are destroyed, arahantship is attained, and nibbāna is realized.
With regard to nirvana, a distinction is made between a person's experience of nirvana during their life and after their death. These two aspects of nirvana are described as:
Nirvana during life (nirvana with remainder) - indicating the experience of someone who has experienced nirvana in their lifetime but still remains in their physical body.
Nirvana after death (nirvana without remainder) - indicating the experience of nirvana for someone after their death.